Hi Barry--
First, I want to see if I understand what you mean, then I'll take a shot
at some SQL to solve the problem.
I take it you have two tables, "a" and "b". They may look something like
this:
Table: a
------------
id name
--- ------
001 Bob
002 Ted
003 Mary
004 Sandy
Table: b
------------
id
---
002
003
And you want your result table to look something like:
id name selected
--- ------ --------
001 Bob 0
002 Ted 1
003 Mary 1
004 Sandy 0
What you're trying to do is not very set-oriented (SQL is very
set-oriented), so how about gathering the two sets you're talking about and
returning the union of the two?
Something like:
select a.id as id, name, 1 as selected from a, b where a.id = b.id union
select a.id as id, name, 0 as selected from a where a.id NOT IN (select id
from b);
There are undoubtedly other ways to do this, but the above query works on
an old PostgreSQL installation I mess around with sometimes.
Hope this helps.
Doug
At 02:30 PM 8/16/01 -0700, Barry Prentiss wrote:
>Hi,
> Here's another SQL query problem:
>
>How do I construct a query that returns 1 if a value is present and zero if
>it is not, for a list of values returned in another query?
>
>i.e. select a.id, a.name, c.selected from table-with-id-and-name a,
> (select 1 as selected from another-table b if a.id = b.id
> or select 0 as selected from another-table b if a.id != b.id ) c;
>
> Thx in Advance,
> Barry Prentiss
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