How to get the count of source records doing UPDATE with joined tables.

I have an sql like this in my stored procedure.
UPDATE T1
SET COL1 = T2.COL1
FROM T1, T2
WHERE T1.COL2=T2.COL2
So, COL1 of T1 table is modified when T1 finds matching records in T2
table with T1.COL2=T2.COL2. The problem is T1.COL1 is updated when
there are multiple matching records from T2. I want to make T1 table
be updated when there is exactly one matching record in T2.
Of course I can check the count of the matching records in T2 before
doing the above but T2 is actually from openquery interface(so dynamic
sql) to a remote server and I don't know exactly how I can get a
cursor with a dynamic sql.(I guess I should search this soon.)
If there is a way to find out the count of matching source records for
the above sql, it will help me a lot. Thanks..I think this should work
UPDATE T1
SET COL1 = T2.COL1
FROM T1, T2
WHERE T1.COL2=T2.COL2
And (Select Count(*) From T2 Where T2.COL2=T1.COL2)=1
Dmitriy
"Yi, Dong-ryon" <feeva@.hanmail.net> wrote in message
news:bf8bb96c.0503131958.770f80ea@.posting.google.com...
>I have an sql like this in my stored procedure.
> UPDATE T1
> SET COL1 = T2.COL1
> FROM T1, T2
> WHERE T1.COL2=T2.COL2
> So, COL1 of T1 table is modified when T1 finds matching records in T2
> table with T1.COL2=T2.COL2. The problem is T1.COL1 is updated when
> there are multiple matching records from T2. I want to make T1 table
> be updated when there is exactly one matching record in T2.
> Of course I can check the count of the matching records in T2 before
> doing the above but T2 is actually from openquery interface(so dynamic
> sql) to a remote server and I don't know exactly how I can get a
> cursor with a dynamic sql.(I guess I should search this soon.)
> If there is a way to find out the count of matching source records for
> the above sql, it will help me a lot. Thanks..|||On 13 Mar 2005 19:58:20 -0800, Yi, Dong-ryon wrote:

>I have an sql like this in my stored procedure.
>UPDATE T1
>SET COL1 = T2.COL1
>FROM T1, T2
>WHERE T1.COL2=T2.COL2
>So, COL1 of T1 table is modified when T1 finds matching records in T2
>table with T1.COL2=T2.COL2. The problem is T1.COL1 is updated when
>there are multiple matching records from T2. I want to make T1 table
>be updated when there is exactly one matching record in T2.
>Of course I can check the count of the matching records in T2 before
>doing the above but T2 is actually from openquery interface(so dynamic
>sql) to a remote server and I don't know exactly how I can get a
>cursor with a dynamic sql.(I guess I should search this soon.)
>If there is a way to find out the count of matching source records for
>the above sql, it will help me a lot. Thanks..
Hi Yi,
As an alternative to the suggestion made by Dmitriy, here's a version
that refers to the T2 table in only one place:
UPDATE T1
SET Col1 = T2a.Col1
FROM T1
INNER JOIN (SELECT Col2, MIN(Col1) AS Col1
FROM T2
GROUP BY Col2
HAVING COUNT(*) = 1) AS T2a
ON T2a.Col2 = T1.Col2
(untested)
Best, Hugo
--
(Remove _NO_ and _SPAM_ to get my e-mail address)