Re: PL/pgSQL 2
| От | Pavel Stehule |
|---|---|
| Тема | Re: PL/pgSQL 2 |
| Дата | |
| Msg-id | CAFj8pRAsh=CwLcKny_RPKitLn7Mx05GFW2vVGXGaAXrZQK8TrQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: PL/pgSQL 2 (David G Johnston <david.g.johnston@gmail.com>) |
| Список | pgsql-hackers |
2014-09-03 21:01 GMT+02:00 David G Johnston <david.g.johnston@gmail.com>:
This is more of an SQL request the pl/pgsql but is/has there been thought to
adding the ternary if/then opeator? Something like:
boolean_exp ?> val_if_true : val_if_false
using "?" by itself would be OK but not ideal - and the addition of the ">"
doesn't seem hateful...
Sorry if this is deemed off-topic but I just went to write
CASE WHEN boolean_exp THEN val_if_true ELSE val_if_false END
And the fact there is as much standard code as there is custom bothered me
just as is being discussed on this thread.
I'm going to go write a "ifthen(bool, anyelement, anyelement)" function
now....
if you use a SQL (SQL macro, then it can be effective)
postgres=# CREATE OR REPLACE FUNCTION if(bool, anyelement, anyelement) RETURNS anyelement AS $$SELECT CASE WHEN $1 THEN $2 ELSE $3 END $$ LANGUAGE sql;
CREATE FUNCTION
postgres=# CREATE OR REPLACE FUNCTION fx(text) RETURNS text AS $$ BEGIN RAISE NOTICE '%', $1; RETURN $1; END$$ LANGUAGE plpgsql;
CREATE FUNCTION
postgres=# SELECT if(false, fx('msg1'), fx('msg2'));
NOTICE: msg2
if
------
msg2
(1 row)
postgres=# SELECT if(true, fx('msg1'), fx('msg2'));
NOTICE: msg1
if
------
msg1
(1 row)
postgres=# CREATE OR REPLACE FUNCTION if(bool, anyelement, anyelement) RETURNS anyelement AS $$SELECT CASE WHEN $1 THEN $2 ELSE $3 END $$ LANGUAGE sql;
CREATE FUNCTION
postgres=# CREATE OR REPLACE FUNCTION fx(text) RETURNS text AS $$ BEGIN RAISE NOTICE '%', $1; RETURN $1; END$$ LANGUAGE plpgsql;
CREATE FUNCTION
postgres=# SELECT if(false, fx('msg1'), fx('msg2'));
NOTICE: msg2
if
------
msg2
(1 row)
postgres=# SELECT if(true, fx('msg1'), fx('msg2'));
NOTICE: msg1
if
------
msg1
(1 row)
Only necessary parameters are evaluated
Pavel
David J.
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