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Re: SQL CASE Statements

From: "Dmitri Bichko" <dbichko(at)aveopharma(dot)com>
To: "Lane Van Ingen" <lvaningen(at)esncc(dot)com>,<pgsql-sql(at)postgresql(dot)org>
Subject: Re: SQL CASE Statements
Date: 2005-08-19 01:56:17
Message-ID: F18A6F7CF1661F46920F2CF713122FED46CC6E@mail.aveo.aveopharma.com (view raw or flat)
Thread:
Lists: pgsql-sql
I am not sure what you are asking...

SELECT CASE WHEN EXISTS (SELECT foo FROM bar WHERE baz = 'a') THEN 1
ELSE 0 END;

Or

SELECT CASE WHEN 'a' = ANY (SELECT froo FROM bar) THEN 1 ELSE 0 END;

Both work, but that's pretty much what you had already - am I missing
what you are trying to achieve?

Though both are likely to be quite inefficient if you are looking up
many values.

Maybe something like:

SELECT f.a, CASE WHEN b.a IS NOT NULL THEN 1 ELSE 0 END
FROM foo f LEFT JOIN bar b USING (a)

Assuming "foo" has the values you want to look up, and "bar" is the
table you check for existence.

Dmitri

> -----Original Message-----
> From: pgsql-sql-owner(at)postgresql(dot)org 
> [mailto:pgsql-sql-owner(at)postgresql(dot)org] On Behalf Of Lane Van Ingen
> Sent: Thursday, August 18, 2005 9:32 PM
> To: pgsql-sql(at)postgresql(dot)org
> Subject: [SQL] SQL CASE Statements
> 
> 
> In the following CASE statement, is it possible to put a 
> SELECT ... WHERE EXISTS in the <condition> of a CASE 
> statement, and have it work?
> 
> The <condition> I want to do is to yield a result of '1' if 
> the statement finds the value 'a' in a table (EXISTS 
> evaluates true), and '0' if it evaluates false ('a' not found).
> 
> SELECT a,
>   CASE WHEN <CONDITION> THEN 1
>        ELSE 0
>   END
> 
> Has anybody done this? If so, can you send me a sample?
> 
> 
> 
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Subject: SQL CASE Statements

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