|The PostgreSQL 9.0 Reference Manual - Volume 1A - SQL Language Reference
by The PostgreSQL Global Development Group
Paperback (6"x9"), 454 pages
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5.3.2 Column Labels
The entries in the select list can be assigned names for subsequent
processing, such as for use in an
ORDER BY clause
or for display by the client application. For example:
SELECT a AS value, b + c AS sum FROM ...
If no output column name is specified using
the system assigns a default column name. For simple column references,
this is the name of the referenced column. For function
calls, this is the name of the function. For complex expressions,
the system will generate a generic name.
AS keyword is optional, but only if the new column
name does not match any
PostgreSQL keyword (see appendix C SQL Key Words). To avoid an accidental match to
a keyword, you can double-quote the column name. For example,
VALUE is a keyword, so this does not work:
SELECT a value, b + c AS sum FROM ...
but this does:
SELECT a "value", b + c AS sum FROM ...
For protection against possible
future keyword additions, it is recommended that you always either
AS or double-quote the output column name.
Note: The naming of output columns here is different from that done in the
FROMclause (see section 220.127.116.11 Table and Column Aliases). It is possible to rename the same column twice, but the name assigned in the select list is the one that will be passed on.
|ISBN 9781906966041||The PostgreSQL 9.0 Reference Manual - Volume 1A - SQL Language Reference||See the print edition|