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GNU Sqltutor

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Introduction

GNU Sqltutor is a web based interactive tutorial of Structured Query Language (SQL). You can try Sqltutor online from

First, a tutorial must be selected from the opening page and started. A series of tutorial questions follows in a simple dialog. When finished Sqltutor displays final evaluation with the review of all questions asked during the session together with user’s SQL queries and correct answers for wrong solutions.

Sqltutor is implemented on the top of a relational database system PostgreSQL. The project consists in part of a C++ program of the same name ‘sqltutor’ released under the GNU General Public License (GNU GPL). The ‘sqltutor’ program is a CGI script that selects SQL questions from its database, checks the answers and evaluates the final score. The second part of the project is a free collection of SQL questions and answers representing SQL tutorials. Sqltutor enables to run one or more tutorials in different languages from a single database.

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0.1 SQLzoo

Sqltutor was inspired by an interactive tutorial SQLzoo by Andrew Cumming from the School of Computing, Napier University, Edinburg, UK. Implementation of the database and the ‘sqltutor’ program is not dependent neither derived from the SQLzoo tutorial.

English SQLzoo tutorial distributed with Sqltutor is based on the collection of SQL questions and answers and datasets from http://sqlzoo.net/. We would like to thank Andrew Cumming for his kind approval to use his data and tutorials in our project.

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1. The Concepts of Sqltutor

This chapter introduces basic concepts of Sqltutor project.

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1.1 Tutorial Dialog

Sqltutor dialog consists of three main pages: opening dialog, tutorial and final evaluation page. Tutorial dialog is designed to be as simple as possible and is based on the very basic HTML constructs so it hopefully should run safely on any web browser. The dialog is going to be described on a case of trivial session in which we answer one simple SQL query.

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1.1.1 Opening Dialog

From the drop down list tutorial must be selected from the opening dialog page. Other options are optional.

Figure 1.1: Opening dialog

Tutorial

Mandatory selection of the SQL tutorial.

Continue

Press the Continue button to open new session and start the selected tutorial.

Display datasets

For the selected tutorial displays the table of available datasets, tables and columns. Datasets are ordered by number of columns.

User
Password

Unused in the current version.

Min points
Max points

Options to limit the tutorial questions according to their point rating.

Help

When checked, help button is displayed during the dialog, where help displays the correct answer(s) for the given tutorial question.

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1.1.2 Tutorial Dialog

Tutorial dialog page displays selected tutorial question, its corresponding tables an their columns and text area for entering SQL code.

Figure 1.2: Tutorial dialog

Execute SQL

Executes SQL query written in the text area edit component, evaluates the result (correct or wrong answer) and displays the resulting rows. Only correct answers are registered, user can execute his/her query as many times as needed for getting a correct solution.

Display data

Display rows for all tables from the given dataset. Number of rows or a table is limited to 50 for larger tables.

Help

This button is available if help was checked in the Opening dialog page. When clicked, Sqltutor displays one or more correct SQL queries for the given question.

Next question

Next tutorial question. If all questions has been answered, tutorial is ended.

Finish test

Close the session and go to the final evaluation page and close the test.

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1.1.3 Evaluation page

Evaluation page contains only one dialog button

New test

Close the evaluation page and return to the new seession opening dialog.

Evaluation page presents the basic review of the closed session: elapsed time, session number, number of questions. correct answers, total points from correct answers and session evaluation. The final evaluation is calculated as the number of correct points multiplied by ratio of correct to all questions reduce by penalty points for wrong and missing answers. Penalty points are defined as a Fibonacci series 1, 2, 3, 5, 8, ... .

All questions from the session dataset tables and answers are shown at the evaluation page. For wrong answers correct solution is also given. For each question internal id and the number of points is displayed in green font for correct answers and red for wrong or missing queries.

Figure 1.3: Evaluation page

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When tutorial is selected from the opening dialog page and started a new session is opened. Sessions record all options selected in the opening dialogue, the start time and the session status which can be open or closed. Session is closed when the tutorial dialogue is regularly finished.

All questions asked during the tutorial sessions are recorded keeping the track of your SQL answered queries. Number of tries during tutorial dialog is not relevant for the final evaluation, only the latest solution is recorded. An answer is registered when Execute SQL, Next question or Finish test button is pressed.

Each question registered in the tutorial database has a point evaluation. Trivial questions are rated by 1 point, nontrivial questions can have point rating up to 15 points. For each question one or more correct answer is stored in the database. When help is enabled during opening dialog, correct answers are displayed when help button is pressed.

Questions are asked about data from datasets, where dataset is one or more SQL tables. Datasets can be shared by different tutorials. Sqltutor selects questions in random manner, starting from easy ones to nontrivial. (1)

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1.2.1 Final evaluation

Final evaluation of sessions is calculated as p \times (c / t), where p is the sum of points for correct answers, c is the number of correct answers and t is the number of all questions asked.

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2. How to install Sqltutor

Sqltutor is a CGI script and a PostgreSQL database of SQL tutorials, collections of SQL questions and answers.

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2.1 How to get Sqltutor

The project is hosted at the Savannah software forge

A copy of the Sqltutor can be get by anonymous GIT access

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2.2 Installer script

Under most circumstances installing Sqltutor is a very simple process and takes only answering a few questions to be completed. The whole installation is guided by sqltutor-install.sh script found in Sqltutor git repository.

 $./sqltutor-install.sh  To run the script you need to have sudo installed and must be listed in the list of users which may execute sudo (sudoers). The user running the script needs also rights to create PostgreSQL databases and create and maintain database roles. Installer calls script autogen.sh to create standard configure script, patches implicit settings and finally installs database, CGI script, info files and datasets and tutorials. Figure 2.1: Installer script  [ < ] [ > ] [ << ] [ Up ] [ >> ] [Top] [Contents] [Index] [ ? ] 2.3 How to change implicit settings All Sqltutor database objects are defined in the SCHEMA sqltutor. Five output variables are defined in ‘configure.ac’ with the following implicit values. SQLTUTOR_DATABASE=sqltutor PostgreSQL database name used by Sqltutor. SQLTUTOR_WWW_USER=sqlquiz WWW user for CGI script sqlutor with full access rights to all tables. SQLTUTOR_PASSWORD=sqlkrok Password for CGI script for the user SQLTUTOR_WWW_USER SQLTUTOR_WWW_EXEC=sqlexec Database role used for running queries entered by users. SQLTUTOR_WWW_EXEC is granted SLECT to datasets’ tables and revoked all rigths on all other sqltutor tables. SQLTUTOR_PASSEXEC=sqlkrok Password for CGI script for the user SQLTUTOR_WWW_EXEC (implicitly the same password as for SQLTUTOR_WWW_USER). These macros are used by all modules and you can change their implicit values if needed in the ‘configure.ac’ file.  [ < ] [ > ] [ << ] [ Up ] [ >> ] [Top] [Contents] [Index] [ ? ] 2.4 Creating the database To create a database, the PostgreSQL server must be up and running. Database is created with SQL command  CREATE DATABASE SQLTUTOR_DATABASE  Two database roles must be created for Sqltutor with SQL command CREATE ROLE  CREATE ROLE SQLTUTOR_WWW_USER LOGIN; CREATE ROLE SQLTUTOR_WWW_EXEC LOGIN;  To set passwords for these new roles run psql and enter SQL ALTER command  ALTER USER SQLTUTOR_WWW_USER WITH PASSWORD 'xxx'; ALTER USER SQLTUTOR_WWW_EXEC WITH PASSWORD 'yyy';  or passwords can be set directly when creating roles  CREATE ROLE SQLTUTOR_WWW_USER PASSWORD 'xxx' LOGIN; CREATE ROLE SQLTUTOR_WWW_EXEC PASSWORD 'yyy' LOGIN;  If PostgreSQL language is not defined in datatabase template1 you must create it explicitly in the Sqltutor database  su - su - postgres psql SQLTUTOR_DATABASE CREATE LANGUAGE plpgsql;   [ < ] [ > ] [ << ] [ Up ] [ >> ] [Top] [Contents] [Index] [ ? ] 2.5 Building and installing Sqltutor To create all Makefiles needed for building binary CGI script ‘sqltutor’, populating Sqltutor database and making info manual go to Sqltutor home directory and run   ./autogen.sh  to create a ‘configure’ script (if it is not allready present) and then   ./configure --bindir=/usr/lib/cgi-bin [ --infodir=/usr/share/info ]  Parameter --bindir defines to which directory CGI script ‘sqltutor’ will be installed. For general information on using GNU autotool see the standard Basic Installation instructions in the ‘INSTALL’. Sqltutor CGI binary with info manual is installed and the database is populated by running  make DESTDIR=install_root_directory install  from the main source directory. Parameter DESTDIR is optional and defines a root directory into which binary ‘sqltutor’ and ‘sqltutor.info’ will be installed. This parameter is needed if you do not have access ritght for writing to ‘/usr/local/cgi-bin’ and ‘/usr/share/info’ (implicit values).  [ < ] [ > ] [ << ] [ Up ] [ >> ] [Top] [Contents] [Index] [ ? ] 2.6 Populating tutorials and datasets Tutorials and dataset are stored in a separate git repository Because ‘configure’ script is not included in the repository, you have to create it first  $ ./autogen 

Then run

 $./configure$ make install 

and that’s all. Datasets and tutorial can be reinstalled as many times as needed.

To enable postgis extension, you must create geometry type in your database (sqltutor in the following example)

 $su # su postgres$ psql -d sqltutor -f /usr/share/postgresql/8.4/contrib/postgis-1.5/postgis.sql $psql -d sqltutor -f /usr/share/postgresql/8.4/contrib/postgis-1.5/spatial_ref_sys.sql  and explicitly enable postgis tutorials  $ ./configure --enable-postgis $make install  PostGIS geometry type must be created by a superuser, because normal users do not have permissions to create C procedures in a database.  [ < ] [ > ] [ << ] [ Up ] [ >> ] [Top] [Contents] [Index] [ ? ] 3. Internals Sqltutor schema is design to enable multiligual translations of tutorial questions with common problem atributes and SQL solutions (anwers). For a given problem one or more questions can be defined with one or more possible solutions. A dataset is a set of problems with given point evaluation and a common set of tables. Tutorials are defined as selections of datasets. Figure 3.1: Sqltutor database schema Tutorials, datasets and problems are defined in SQL language with a set of stored procedures. An example of how to define a dataset is given a file compute_store.sql with description of all steps in the comments.  [ < ] [ > ] [ << ] [ Up ] [ >> ] [Top] [Contents] [Index] [ ? ] 3.1 How to add new dataset To define a dataset we have to introduce its name (function init_dataset and optionaly describe its data source or sources (function add_ds_source). Dataset tables are described by calls to function add_ds_table where parameters are dataset name, priority in which tables are listed in tutorail questions, table name and the list of its column names (attributes). Example:  SELECT init_dataset ('computer_store'); SELECT add_ds_source('computer_store', 2010, 'http://en.wikibooks.org/wiki/SQL_Exercises/The_computer_store'); SELECT add_ds_table ('computer_store', 1, 'manufacturers', 'code, name'); SELECT add_ds_table ('computer_store', 2, 'products', 'code, name, price, manufacturer');  For each problem we can formulate one or more quesitions and one or more answers (sql queries). Within a dataset each problem is described by a unique identification number (secon parameter of the function insert_problem) followed by its point rating.  -- dataset name, internal problem_id, points, category -- (currently unused) SELECT insert_problem ('computer_store', 10, 1, 'select'); -- dataset name, internal problem id, order, language, question text SELECT insert_question('computer_store', 10, 1, 'en', 'Select the names and the prices of all the products in the store.'); -- dataset name, internal dataset id, order, language, sql answer SELECT insert_answer ('computer_store', 10, 1, 'SELECT name FROM products;');  Tutoriual questions can be translated to other languages.  -- Problem defines id, point rating and category SELECT insert_problem ('computer_store', 30, 2, 'select'); SELECT insert_question('computer_store', 30, 1, 'en', 'Select the names of the products with a price less than or equal to$200.'); SELECT insert_answer ('computer_store', 30, 1, 'SELECT name FROM products WHERE price <= 200;'); -- Czech translation of problem id 30. Answers (SQL code) are shared -- among all translations SELECT insert_question('computer_store', 30, 1, 'cs', 'Vypište jména všech produktů, jejichž cena je menší nebo rovna 200 dolarů.'); 

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3.2 How to add new tutorial

A tutorial definition is simple, we introduce its language and name and add to it selected datasets.

 SELECT init_tutorial ('en', 'Demo'); SELECT insert_dataset('Demo', 'en', 'computer_store'); SELECT init_tutorial ('cs', 'Demo'); SELECT insert_dataset('Demo', 'cs', 'computer_store'); 

Tutorials can be easily deleted. Datasets are independent on tutorials and they are not affected in any way when a tutorial referencing to them is deleted.

 SELECT delete_tutorial('cs', 'Demo'); 

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3.3 Doxygen

Doxygen generated source documentation is available only partly for classes implementing CGI interface for Sqltutor. Change to directory ‘doc’ and run ‘make doxygen’. Generated output is stored in directories ‘html’ and ‘latex’.

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You may not propagate or modify a covered work except as expressly provided under this License. Any attempt otherwise to propagate or modify it is void, and will automatically terminate your rights under this License (including any patent licenses granted under the third paragraph of section 11).

However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, you do not qualify to receive new licenses for the same material under section 10.

10. Acceptance Not Required for Having Copies.

You are not required to accept this License in order to receive or run a copy of the Program. Ancillary propagation of a covered work occurring solely as a consequence of using peer-to-peer transmission to receive a copy likewise does not require acceptance. However, nothing other than this License grants you permission to propagate or modify any covered work. These actions infringe copyright if you do not accept this License. Therefore, by modifying or propagating a covered work, you indicate your acceptance of this License to do so.

11. Automatic Licensing of Downstream Recipients.

Each time you convey a covered work, the recipient automatically receives a license from the original licensors, to run, modify and propagate that work, subject to this License. You are not responsible for enforcing compliance by third parties with this License.

An “entity transaction” is a transaction transferring control of an organization, or substantially all assets of one, or subdividing an organization, or merging organizations. If propagation of a covered work results from an entity transaction, each party to that transaction who receives a copy of the work also receives whatever licenses to the work the party’s predecessor in interest had or could give under the previous paragraph, plus a right to possession of the Corresponding Source of the work from the predecessor in interest, if the predecessor has it or can get it with reasonable efforts.

You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License. For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it.

12. Patents.

A “contributor” is a copyright holder who authorizes use under this License of the Program or a work on which the Program is based. The work thus licensed is called the contributor’s “contributor version”.

A contributor’s “essential patent claims” are all patent claims owned or controlled by the contributor, whether already acquired or hereafter acquired, that would be infringed by some manner, permitted by this License, of making, using, or selling its contributor version, but do not include claims that would be infringed only as a consequence of further modification of the contributor version. For purposes of this definition, “control” includes the right to grant patent sublicenses in a manner consistent with the requirements of this License.

Each contributor grants you a non-exclusive, worldwide, royalty-free patent license under the contributor’s essential patent claims, to make, use, sell, offer for sale, import and otherwise run, modify and propagate the contents of its contributor version.

In the following three paragraphs, a “patent license” is any express agreement or commitment, however denominated, not to enforce a patent (such as an express permission to practice a patent or covenant not to sue for patent infringement). To “grant” such a patent license to a party means to make such an agreement or commitment not to enforce a patent against the party.

If you convey a covered work, knowingly relying on a patent license, and the Corresponding Source of the work is not available for anyone to copy, free of charge and under the terms of this License, through a publicly available network server or other readily accessible means, then you must either (1) cause the Corresponding Source to be so available, or (2) arrange to deprive yourself of the benefit of the patent license for this particular work, or (3) arrange, in a manner consistent with the requirements of this License, to extend the patent license to downstream recipients. “Knowingly relying” means you have actual knowledge that, but for the patent license, your conveying the covered work in a country, or your recipient’s use of the covered work in a country, would infringe one or more identifiable patents in that country that you have reason to believe are valid.

If, pursuant to or in connection with a single transaction or arrangement, you convey, or propagate by procuring conveyance of, a covered work, and grant a patent license to some of the parties receiving the covered work authorizing them to use, propagate, modify or convey a specific copy of the covered work, then the patent license you grant is automatically extended to all recipients of the covered work and works based on it.

A patent license is “discriminatory” if it does not include within the scope of its coverage, prohibits the exercise of, or is conditioned on the non-exercise of one or more of the rights that are specifically granted under this License. You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software, under which you make payment to the third party based on the extent of your activity of conveying the work, and under which the third party grants, to any of the parties who would receive the covered work from you, a discriminatory patent license (a) in connection with copies of the covered work conveyed by you (or copies made from those copies), or (b) primarily for and in connection with specific products or compilations that contain the covered work, unless you entered into that arrangement, or that patent license was granted, prior to 28 March 2007.

Nothing in this License shall be construed as excluding or limiting any implied license or other defenses to infringement that may otherwise be available to you under applicable patent law.

13. No Surrender of Others’ Freedom.

If conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot convey a covered work so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not convey it at all. For example, if you agree to terms that obligate you to collect a royalty for further conveying from those to whom you convey the Program, the only way you could satisfy both those terms and this License would be to refrain entirely from conveying the Program.

14. Use with the GNU Affero General Public License.

Notwithstanding any other provision of this License, you have permission to link or combine any covered work with a work licensed under version 3 of the GNU Affero General Public License into a single combined work, and to convey the resulting work. The terms of this License will continue to apply to the part which is the covered work, but the special requirements of the GNU Affero General Public License, section 13, concerning interaction through a network will apply to the combination as such.

15. Revised Versions of this License.

The Free Software Foundation may publish revised and/or new versions of the GNU General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

Each version is given a distinguishing version number. If the Program specifies that a certain numbered version of the GNU General Public License “or any later version” applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of the GNU General Public License, you may choose any version ever published by the Free Software Foundation.

If the Program specifies that a proxy can decide which future versions of the GNU General Public License can be used, that proxy’s public statement of acceptance of a version permanently authorizes you to choose that version for the Program.

16. Disclaimer of Warranty.

THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

17. Limitation of Liability.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

18. Interpretation of Sections 15 and 16.

If the disclaimer of warranty and limitation of liability provided above cannot be given local legal effect according to their terms, reviewing courts shall apply local law that most closely approximates an absolute waiver of all civil liability in connection with the Program, unless a warranty or assumption of liability accompanies a copy of the Program in return for a fee.

How to Apply These Terms to Your New Programs

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively state the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found.

 one line to give the program's name and a brief idea of what it does. Copyright (C) year name of author This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/. 

Also add information on how to contact you by electronic and paper mail.

If the program does terminal interaction, make it output a short notice like this when it starts in an interactive mode:

 program Copyright (C) year name of author This program comes with ABSOLUTELY NO WARRANTY; for details type ‘show w’. This is free software, and you are welcome to redistribute it under certain conditions; type ‘show c’ for details. 

The hypothetical commands ‘show w’ and ‘show c’ should show the appropriate parts of the General Public License. Of course, your program’s commands might be different; for a GUI interface, you would use an “about box”.

You should also get your employer (if you work as a programmer) or school, if any, to sign a “copyright disclaimer” for the program, if necessary. For more information on this, and how to apply and follow the GNU GPL, see http://www.gnu.org/licenses/.

The GNU General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License. But first, please read http://www.gnu.org/philosophy/why-not-lgpl.html.

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A. Copying This Manual

Version 1.3, 3 November 2008

 Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. http://fsf.org/ Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. 
1. PREAMBLE

The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

2. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document’s overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work’s title, preceding the beginning of the body of the text.

The “publisher” means any person or entity that distributes copies of the Document to the public.

A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.

The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

3. VERBATIM COPYING

You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and you may publicly display copies.

4. COPYING IN QUANTITY

If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document’s license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

5. MODIFICATIONS

You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
4. Preserve all the copyright notices of the Document.
6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document’s license notice.
8. Include an unaltered copy of this License.
9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
15. Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version’s license notice. These titles must be distinct from any other section titles.

You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

6. COMBINING DOCUMENTS

You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”

7. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

8. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

9. TRANSLATION

Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

10. TERMINATION

You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.

11. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy’s public statement of acceptance of a version permanently authorizes you to choose that version for the Document.

12. RELICENSING

“Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.

“Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.

An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

  Copyright (C) year your name. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License''. 

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with…Texts.” line with this:

  with the Invariant Sections being list their titles, with the Front-Cover Texts being list, and with the Back-Cover Texts being list. 

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.

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Index

Index Entry Section how to install 2. How to install Sqltutor internals 3. Internals introduction Introduction

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Footnotes

(1)

If you explicitly chose min/max value of points and/or dataset during opening dialog, questions are selected simply in random.

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This document was generated by Ales Cepek on May 25, 2014 using texi2html 1.82.

The buttons in the navigation panels have the following meaning:

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[ < ] Back Previous section in reading order 1.2.2
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where the Example assumes that the current position is at Subsubsection One-Two-Three of a document of the following structure:

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