Question

I have a procedure that gets a sql query in string. Example:

SELECT SUM(Refuse) FROM FOOD_DES WHERE Refuse > 1

but I need sum only that rows for which condition is satisfied.
Condition looks like:

CONVERT(INT,RAND() * 100 ) <= @probability

but this doesnt work (it sums all elements):

SELECT SUM(Refuse) FROM FOOD_DES WHERE Refuse > 1 AND
CONVERT(INT,RAND() * 100 ) <= @probability

So tried next:

SELECT SUM(Refuse) FROM FOOD_DES  AS T CROSS APPLY fn_probability() AS F

CREATE FUNCTION fn_probability ( )
RETURNS @probabilityInfo TABLE ( Result INT )
AS 
    BEGIN 
        DECLARE @rand INT
        SET @rand = ( SELECT TOP 1
                                RandValue
                      FROM      RandView
                    )
        IF @rand <= 80 
            INSERT  INTO @probabilityInfo
                    ( Result )
            VALUES  ( 1 )
        RETURN  
    END

CREATE VIEW RandView
AS 
SELECT CONVERT(INT, RAND() * 100) AS RandValue

But it doesnt work neither.
Any idea?:)

Answer 1

How about like this:

WITH data(Refuse, RandomNumber) AS
(
    SELECT 
        Refuse
        ,CONVERT(INT, RAND(CHECKSUM(NEWID())) * 100) 
    FROM 
        FOOD_DES
    WHERE 
        Refuse > 1
)
SELECT
    SUM(Refuse) 
FROM
    data
WHERE
    RandomNumber <= @probability