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Conditionally executing multiple statements in series as single SQL statement

From: Nathaniel Trellice <naptrel(at)yahoo(dot)co(dot)uk>
To: pgsql-novice(at)postgresql(dot)org
Subject: Conditionally executing multiple statements in series as single SQL statement
Date: 2009-12-18 13:01:58
Message-ID: 95970.29891.qm@web25008.mail.ukl.yahoo.com (view raw or flat)
Thread:
Lists: pgsql-novice
Hi all,

In C, and many other programming languages, statements like the following are popular:

int status = (do_first_thing() && do_second_thing() && do_third_thing() && do_fourth_thing());

With this kind of expression, the program calls the function 'do_first_thing'. If, and only if, that returns non-zero, 'do_second_thing' will be executed. Again, if and only if that returns non-zero, 'do_third_thing' is executed. Etc.

In other words, later statements will only be executed if all before them have 'gone well'. When a statement 'fails', no further expressions are executed.. The variable 'status' is non-zero if, and only if, all four things were successfully executed.

For convenience, I'd really like to be able to achieve similar behaviour within an SQL statement, i.e. present multiple statements (such as INSERT statements) and only execute the later ones if the earlier ones have been executed without error. And I'd like to be able to present all the statements within a single, compound SQL statement to the database.

Is such a thing possible, using any fancy SQL syntactic tricks?


Nathaniel



      


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Subject: Re: Conditionally executing multiple statements in series as single SQL statement
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