Question

I created a stored procedure to update only the rows of a table that have changed

I used the SQLSERVER coalesce function.

CREATE PROCEDURE update_only_changed

            @FName varchar(50) = NULL,

            @LName varchar(50) = NULL,

            @CUST_DB VARCHAR(20) 

AS

BEGIN

            DECLARE @QUERY VARCHAR(255)

            SET @QUERY = 'UPDATE ' + @CUST_DB + '..people SET LastName = COALESCE(@LName, LastName) WHERE id = 1'

            EXEC (@QUERY)

END

GO

Some considerations

• Is a dynamic sql

• The name of the database is passed as a parameter in the procedure

So, When I run the sql I have two situations:

• EXEC(@ QUERY):

  I get the error saying: Must declare the scalar variable "@ LName".
  it does not interpret the variable that the command coalesce
  

• EXEC @QUERY (without parentheses)

   I get the error saying: The database 'UPDATE CUSTOMER' does not exist. Make sure the name is spelled correctly.
  

how can i put that to work ?

Remember, if a run the procedure with the update statement static, without EXEC, it works

UPDATE CUSTOMER..people SET LastName = COALESCE(@LName, LastName) WHERE id = 1

Answer 1

The first one doesn’t work because there is no variable @Lname in the context of the exec – it only exists in your procedure’s scope. You need to pass it into the scope of the query by using sp_executesql instead of exec

exec sp_executesql @query, N'@LName varchar(50)', @Lname

BUT

I wouldn’t recommend doing anything at all like this.