Question

I have a stored procedure that is dynamically building a query. The where clause associated with this query is based on filter values selected by a user. No matter what I do though, the where clause does not seem to get set.

-- Dynamically build the WHERE clause based on the filters
DECLARE @whereClause as nvarchar(1024)
IF (@hasSpouse > -1)
BEGIN
  IF (@hasSpouse = 0)
    SET @whereClause='p.[HasSpouse]=0'
  ELSE
    SET @whereClause='(p.[HasSpouse]=1 OR p.[HasSpouse] IS NULL)'
  END

  -- Dynamically add the next filter if necessary
  IF (@isVegan > -1)
  BEGIN
    IF (LEN(@whereClause) > 0)
    BEGIN
      SET @whereClause = @whereClause + ' AND '
    END

    IF (@isVegan = 0)
      SET @whereClause = @whereClause + 'c.[IsVegan]=0'
    ELSE
      SET @whereClause = @whereClause + '(c.[IsVegan]=1 OR c.[IsVegan] IS NULL)'
  END

  PRINT @whereClause

The @whereClause never prints anything. In turn, the LEN(@whereClause) is always NULL. The @isVegan and @hasSpouse values are passed into the stored procedure. The values are what I expected.

What am I doing wrong? Why is the @whereClause never being set?

Thank you for your help!

Thank you!

Answer 1

Initialize it first, something + NULL is always NULL

DECLARE @whereClause as nvarchar(1024)
SET @whereClause  = ''