SQL ARRAY IN 'WHERE IN'

Question

Dear All
How could I declare a variable and then used in WHERE IN clause?
I would like to do something like
SELECT * FROM rooms WHERE number IN ('1001','1012','1015')
but with the room number array declared as variable so I could reuse it
I tried the following which is not working
DECLARE @RoomNumbers VARCHAR(MAX) = '1001,1012,1015';SELECT * FROM rooms WHERE number IN (@RoomNumbers)
If not using EXEC, is it possible to do it?  Thanks.

Answer 1

You can do it by creating a split function.  The are many examples of split functions, but one possibility is
CREATE FUNCTION dbo.Split (@DelimitedString nvarchar(max), @Delimiter nvarchar(max))
RETURNS table
AS
RETURN (
WITH Pieces (ID, start, stop) AS (
SELECT CAST(1 AS bigint), CAST(1 AS bigint), CAST(CHARINDEX(@Delimiter, @DelimitedString) AS bigint)
UNION ALL
SELECT ID + 1, CAST(stop + DATALENGTH(@Delimiter)/2 As bigint), CAST(CHARINDEX(@Delimiter, @DelimitedString, stop + DATALENGTH(@Delimiter)/2) AS bigint)
FROM Pieces
WHERE stop > 0
SELECT ID,
SUBSTRING(@DelimitedString, start, CASE WHEN stop > 0 THEN stop-start ELSE LEN(@DelimitedString) END) AS Element
FROM Pieces
GO
Then you can use that split function, for example
DECLARE @RoomNumbers VARCHAR(MAX) = '1001,1012,1015';
SELECT * FROM rooms WHERE number IN (Select Element From dbo.Split(@RoomNumbers, ','))
Tom
Very good, Thanks