How do I set a variable to the result of select query without using a stored procedure?
I want to do something like: OOdate DATETIME
SET OOdate =
You could also just put the first SELECT in a subquery. Since most optimizers will fold it into a constant anyway, there should not be a performance hit on this.
Incidentally, since you are using a predicate like this:
CONVERT(...) = CONVERT(...)
that predicate expression cannot be optimized properly or use indexes on the columns reference by the CONVERT() function.
Here is one way to make the original query somewhat better:
DECLARE @ooDate datetime
SELECT @ooDate = OO.Date FROM OLAP.OutageHours AS OO where OO.OutageID = 1
SELECT
COUNT(FF.HALID)
FROM
Outages.FaultsInOutages AS OFIO
INNER JOIN Faults.Faults as FF ON
FF.HALID = OFIO.HALID
WHERE
FF.FaultDate >= @ooDate AND
FF.FaultDate < DATEADD(day, 1, @ooDate) AND
OFIO.OutageID = 1
This version could leverage in index that involved FaultDate, and achieves the same goal.
Here it is, rewritten to use a subquery to avoid the variable declaration and subsequent SELECT.
SELECT
COUNT(FF.HALID)
FROM
Outages.FaultsInOutages AS OFIO
INNER JOIN Faults.Faults as FF ON
FF.HALID = OFIO.HALID
WHERE
CONVERT(varchar(10), FF.FaultDate, 126) = (SELECT CONVERT(varchar(10), OO.Date, 126) FROM OLAP.OutageHours AS OO where OO.OutageID = 1) AND
OFIO.OutageID = 1
Note that this approach has the same index usage issue as the original, because of the use of CONVERT() on FF.FaultDate. This could be remedied by adding the subquery twice, but you would be better served with the variable approach in this case. This last version is only for demonstration.
Regards.
-- Sql Server 2005 Management studio
use Master
go
DECLARE @MyVar bigint
SET @myvar = (SELECT count(*) FROM spt_values);
SELECT @myvar
Result: 2346 (in my db)
-- Note: @myvar = @Myvar
What do you mean exactly? Do you want to reuse the result of your query for an other query?
In that case, why don't you combine both queries, by making the second query search inside the results of the first one (SELECT xxx in (SELECT yyy...)
You can use something like
SET @cnt = (SELECT COUNT(*) FROM User)
or
SELECT @cnt = (COUNT(*) FROM User)
For this to work the SELECT must return a single column and a single result and the SELECT statement must be in parenthesis.
Edit: Have you tried something like this?
DECLARE @OOdate DATETIME
SET @OOdate = Select OO.Date from OLAP.OutageHours as OO where OO.OutageID = 1
Select COUNT(FF.HALID)
from Outages.FaultsInOutages as OFIO
inner join Faults.Faults as FF
ON FF.HALID = OFIO.HALID
WHERE @OODate = FF.FaultDate
AND OFIO.OutageID = 1
This will work for original question asked:
DECLARE @Result INT;
SELECT @Result = COUNT(*)
FROM TableName
WHERE Condition
You could use:
declare @foo as nvarchar(25)
select @foo = 'bar'
select @foo