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Re: function DECODE and triggers

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On Tue, 2005-10-25 at 00:16 +0200, Rafael Montoya wrote:
> I'm migrating from oracle to postgresl, and i  have these 2 problems:
> 
> 1.
> PostgreSQL doesn't support function DECODE from Oracle, but it can be 
> replicated with
> CASE WHEN expr THEN expr [...] ELSE expr END  , the problem appears when i 
> want to convert this sentence from oracle to postgresl:
>                select decode (pre.C_GEN,'01','M','02','F','') as GENERO
> my convertion is
>               case when  pre.C_GEN = '01' then GENERO='M' else GENERO='F' 
> end ,
> but i dont' know if the assigment of GENERO is correct.

SELECT CASE WHEN re.C_GEN = '01' THEN 'M' ELSE 'F' END AS GENER0

> 2.
> Writing triggers i don't know if postgresql supports statements like this:
>     CREATE OR REPLACE TRIGGER trig
>     AFTER UPDATE OF column2              <<----- Here is the doubt
>     ON table_product
>     FOR EACH ROW
>     BEGIN
>     ...
>     END
> 
> In postgresql:
>    CREATE OR REPLACE TRIGGER trig

CREATE TRIGGER does not support CREATE OR REPLACE

>    AFTER UPDATE OF column2               <<----- is this correct?

No.  PostgreSQL doesn't support column triggers yet.

>    ON table_product
>    FOR EACH ROW EXECUTE PROCEDURE trig();

CREATE TRIGGER trig
   AFTER UPDATE
   ON table_product
   FOR EACH ROW EXECUTE PROCEDURE trig();

In trig() you need to make the action conditional:

    IF NEW.column2 <> OLD.column2 OR 
      (NEW.column2 IS NULL) <> (OLD.column2 IS NULL) THEN
    ...
    END IF;

(assuming it's written in plpgsql).
-- 
Oliver Elphick                                          olly@xxxxxxxxxx
Isle of Wight                              http://www.lfix.co.uk/oliver
GPG: 1024D/A54310EA  92C8 39E7 280E 3631 3F0E  1EC0 5664 7A2F A543 10EA
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