returned value from SQL statement

hi,

i would like to know how can i control the returned value from a SQL statement ?
for example, if i do an INSERT INTO... :
1. how can i know if the INSERT worked ?
i mean i already trapped the unicity violation, but what if there is another error ? where can i get a complete list of exceptions ?

2. if the INSERT INTO is successful, how can i know it ? what is the returned value ?

3. the same question as point 2 but for all SQL statements from PostgreSQL.

I read few books and every time this part is not treated correctly but only partially.

thanks a lot,

--
Alain
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Windows XP SP2
PostgreSQL 8.2.4 / MS SQL server 2005
Apache 2.2.4
PHP 5.2.4
C# 2005-2008