Parameters in Procedure not working

Question

I created the following query:

    SELECT Title, sum(No_Of_Copies) as 'Total Copies'
    FROM BOOK_COPIES bc
    join BOOK_AUTHORS ba
    on bc.BookId=ba.BookId
    join BOOK b
    on b.BookId=bc.BookId
    join LIBRARY_BRANCH lb
    on bc.BranchId=lb.BranchId where AuthorName='George Orwell' and BranchName='Central'
    group by b.Title

From this query I wanted to create a procedure that could search for the amount of book copies of any Author or Branch name, so I created this:

    CREATE PROC GetTotalCopies @AuthorName varchar(100), @BranchName varchar(100)
    AS

       SELECT Title, sum(No_Of_Copies) as 'Total Copies'
       FROM BOOK_COPIES bc
       join BOOK_AUTHORS ba
       on bc.BookId=ba.BookId
       join BOOK b
       on b.BookId=bc.BookId
       join LIBRARY_BRANCH lb
       on bc.BranchId=lb.BranchId where AuthorName='@AuthorName' and BranchName='@BranchName'
       group by b.Title

But when I run it with a Author Name and Branch Name I get empty tables. Anyone know why? I created this database from the following flowchart: https://www.learncodinganywhere.com/learningmanagementsystem/links/07_DB/SQL_Drill.pdf using SQL Server 2008.

Answer 1

No need for single quotes. The arguments are already strings.

So, write the query like this:

where AuthorName = @AuthorName and BranchName = @BranchName

Note: You might want to consider arguments that function as "all values":

where (AuthorName = @AuthorName or @AuthorName is null) and
      (BranchName = @BranchName or @BranchName is null)