There isn't much in it, but it looks the one with IFNULL is the fastest.
Will stick to that one.
RBS
-Original Message-
From: RB Smissaert [mailto:[EMAIL PROTECTED]
Sent: 31 January 2008 21:17
To: sqlite-users@sqlite.org
Subject: RE: [sqlite] Re: how to do this case when?
Thanks; I came up with number 3, but I like your number 1.
Any idea what could be the fastest or will it all be the same?
RBS
-Original Message-
From: Igor Tandetnik [mailto:[EMAIL PROTECTED]
Sent: 31 January 2008 20:59
To: SQLite
Subject: [sqlite] Re: how to do this case when?
RB Smissaert <[EMAIL PROTECTED]>
wrote:
> How do I alter this SQL, so that the original field remains the same
> when
> there is no match? A case when else end should do it, but I can't get
> it
> right.
>
> UPDATE Table1 SET Field1 =
> (SELECT Field2 FROM Table2
> WHERE Table1.Field1 = Table2.Field1)
UPDATE Table1 SET Field1 =
IFNULL(
(SELECT Field2 FROM Table2
WHERE Table1.Field1 = Table2.Field1),
Field1);
-- or
UPDATE Table1 SET Field1 =
(SELECT Field2 FROM Table2
WHERE Table1.Field1 = Table2.Field1
union all select Table1.Field1;
);
-- or
UPDATE Table1 SET Field1 =
(SELECT Field2 FROM Table2
WHERE Table1.Field1 = Table2.Field1)
where exists
(SELECT Field2 FROM Table2
WHERE Table1.Field1 = Table2.Field1)
Igor Tandetnik
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