如何验证列？ SQL

Question

I have a table with some data. One of the columns is named Category and contains data like SKI or SB.

I have a function to validate and a procedure. I need to get only the columns with Category SKI. I know there are other simple ways to implement this...but I have an assignment and this is why I use a function and a procedure.

What am I doing wrong?

CREATE FUNCTION validateProducts(@productCategory NVARCHAR(50))
RETURNS BIT AS
BEGIN
    DECLARE @returnValue BIT
    IF(@productCategory LIKE 'SKI')
        SET @returnValue = 1 --valid
    ELSE
        SET @returnValue = 0 --invalid


    RETURN @returnValue
END
GO

CREATE PROCEDURE usp_ProductsRead(@productType NVARCHAR(50)) AS
BEGIN

    DECLARE @productCategory NVARCHAR(50)
    SET @productCategory=@productType
    SELECT Category, Model
    FROM PRODUCTS
    WHERE dbo.validateProducts(@productCategory) = 1
END
GO

EXEC usp_ProductsRead @productType='SKI'

Answer 1

Add one more condtion in where clause else you will get all the rows from table when you pass @productCategory ='SKI'

CREATE PROCEDURE usp_ProductsRead(@productType NVARCHAR(50)) AS
BEGIN
    SELECT Category, Model
    FROM PRODUCTS
    WHERE dbo.validateProducts(@productType) = 1 and Category=@productType
END
GO

or check the value returned by function then select the PRODUCTS table

CREATE PROCEDURE usp_ProductsRead(@productType NVARCHAR(50)) AS
BEGIN
if (select dbo.validateProducts(@productType))=1
Begin
        SELECT Category, Model
        FROM PRODUCTS
        WHERE Category=@productType
end
else
Begin
     Print 'Category is not SKI'
End

Answer 2

Of course it returns all categories, because your condition in the where is not on the rows in the table. It is on the value being passed in. So, if that value matches, then all rows are returned. If the value doesn't match, then no rows are returned.

You need to run the function on the Cateogry stored in the table. I'm not sure what column that is, but here is a guess:

CREATE PROCEDURE usp_ProductsRead AS
BEGIN
    SELECT p.Category, p.Model
    FROM PRODUCTS p
    WHERE dbo.validateProducts(p.Category) = 1
END;

EXEC dbo.usp_ProductsRead;