|The PostgreSQL 9.0 Reference Manual - Volume 2 - Programming Guide
by The PostgreSQL Global Development Group
Paperback (6"x9"), 478 pages
RRP £14.95 ($19.95)
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9.5.2 Executing a Command With No Result
For any SQL command that does not return rows, for example
INSERT without a
RETURNING clause, you can
execute the command within a PL/pgSQL function
just by writing the command.
Any PL/pgSQL variable name appearing in the command text is treated as a parameter, and then the current value of the variable is provided as the parameter value at run time. This is exactly like the processing described earlier for expressions; for details see section 9.10.1 Variable Substitution.
When executing a SQL command in this way, PL/pgSQL plans the command just once and re-uses the plan on subsequent executions, for the life of the database connection. The implications of this are discussed in detail in section 9.10.2 Plan Caching.
Sometimes it is useful to evaluate an expression or
query but discard the result, for example when calling a function
that has side-effects but no useful result value. To do
this in PL/pgSQL, use the
This executes query and discards the
result. Write the query the same
way you would write an SQL
SELECT command, but replace the
PL/pgSQL variables will be
substituted into the query just as for commands that return no result,
and the plan is cached in the same way. Also, the special variable
FOUND is set to true if the query produced at
least one row, or false if it produced no rows (see
section 9.5.5 Obtaining the Result Status).
Note: One might expect that writing
SELECTdirectly would accomplish this result, but at present the only accepted way to do it is
PERFORM. A SQL command that can return rows, such as
SELECT, will be rejected as an error unless it has an
INTOclause as discussed in the next section.
PERFORM create_mv('cs_session_page_requests_mv', my_query);
|ISBN 9781906966065||The PostgreSQL 9.0 Reference Manual - Volume 2 - Programming Guide||See the print edition|