ef38a4d975
GROUP BY ALL is a form of GROUP BY that adds any TargetExpr that does not contain an aggregate or window function into the groupClause of the query, making it exactly equivalent to specifying those same expressions in an explicit GROUP BY list. This feature is useful for certain kinds of data exploration. It's already present in some other DBMSes, and the SQL committee recently accepted it into the standard, so we can be reasonably confident in the syntax being stable. We do have to invent part of the semantics, as the standard doesn't allow for expressions in GROUP BY, so they haven't specified what to do with window functions. We assume that those should be treated like aggregates, i.e., left out of the constructed GROUP BY list. In passing, wordsmith some existing documentation about GROUP BY, and update some neglected synopsis entries in select_into.sgml. Author: David Christensen <david@pgguru.net> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/CAHM0NXjz0kDwtzoe-fnHAqPB1qA8_VJN0XAmCgUZ+iPnvP5LbA@mail.gmail.com |
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PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.