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This allows the RETURNING list of INSERT/UPDATE/DELETE/MERGE queries to explicitly return old and new values by using the special aliases "old" and "new", which are automatically added to the query (if not already defined) while parsing its RETURNING list, allowing things like: RETURNING old.colname, new.colname, ... RETURNING old.*, new.* Additionally, a new syntax is supported, allowing the names "old" and "new" to be changed to user-supplied alias names, e.g.: RETURNING WITH (OLD AS o, NEW AS n) o.colname, n.colname, ... This is useful when the names "old" and "new" are already defined, such as inside trigger functions, allowing backwards compatibility to be maintained -- the interpretation of any existing queries that happen to already refer to relations called "old" or "new", or use those as aliases for other relations, is not changed. For an INSERT, old values will generally be NULL, and for a DELETE, new values will generally be NULL, but that may change for an INSERT with an ON CONFLICT ... DO UPDATE clause, or if a query rewrite rule changes the command type. Therefore, we put no restrictions on the use of old and new in any DML queries. Dean Rasheed, reviewed by Jian He and Jeff Davis. Discussion: https://postgr.es/m/CAEZATCWx0J0-v=Qjc6gXzR=KtsdvAE7Ow=D=mu50AgOe+pvisQ@mail.gmail.com |
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| configure | ||
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| COPYRIGHT | ||
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| HISTORY | ||
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| README.md | ||
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/.