Column view (see Column view) is normally used to view and edit properties embedded in the hierarchical structure of an Org file. It can be quite useful to use column view also from the agenda, where entries are collected by certain criteria.
To understand how to use this properly, it is important to realize that the entries in the agenda are no longer in their proper outline environment. This causes the following issues:
COLUMNSformat to use. Since the entries in the agenda are collected from different files, and different files may have different
COLUMNSformats, this is a non-trivial problem. Org first checks if the variable
org-agenda-overriding-columns-formatis currently set, and if so, takes the format from there. Otherwise it takes the format associated with the first item in the agenda, or, if that item does not have a specific format (defined in a property, or in its file), it uses
CLOCKSUMproperty. Org will then sum the values displayed in the agenda. In the daily/weekly agenda, the sums will cover a single day; in all other views they cover the entire block. It is vital to realize that the agenda may show the same entry twice (for example as scheduled and as a deadline), and it may show two entries from the same hierarchy (for example a parent and its child). In these cases, the summation in the agenda will lead to incorrect results because some values will count double.
CLOCKSUM, that is always the entire clocked time for this item. So even in the daily/weekly agenda, the clocksum listed in column view may originate from times outside the current view. This has the advantage that you can compare these values with a column listing the planned total effort for a task—one of the major applications for column view in the agenda. If you want information about clocked time in the displayed period use clock table mode (press R in the agenda).
CLOCKSUM_T, that is always today's clocked time for this item. So even in the weekly agenda, the clocksum listed in column view only originates from today. This lets you compare the time you spent on a task for today, with the time already spent (via
CLOCKSUM) and with the planned total effort for it.