Denis Woodbury wrote:
Hi,
I would like to know if this this type of statement can be used in
Postgresql
IF NOT EXISTS (SELECT 1 FROM Table WHERE col1 = 'mystring' )
BEGIN
...
END
PostgreSQL doesn't have any sort of free block flow control; it doesn't
have an IF statement or similar in SQL. You can usually just create a
PL/PgSQL function to do what you want.
It'd occasionally be nice to be able to write PL/PgSQL bodies in-line in
SQL code rather than explicitly creating then dropping a function when
you do need to do something a bit weird (usually in admin/maintenance
scripts) but the current approach does work fine.
It also helps that you can often achieve the required logic with plain,
standard SQL. The CASE statement is particularly useful:
SELECT
CASE
WHEN col1 = 'mystring' THEN [expression or function call]
END
FROM Table;
--
Craig Ringer
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