I need to write a query that returns a result set based on a parameter that is passed to it.My table contains records of customer support calls. For the review of these calls I need to be able to pass in values for the topics of these calls. This can be one or more based on user selection.Here's my table:CREATE TABLE Tbl1 (Customer varchar(50),Country char(3),Topic varchar(50),CallCount int,CallMonth char(10))--Insert records in source table Tbl1INSERT INTO Tbl1 VALUES('10001','MX','Shipping Advise',1,'2011-01')INSERT INTO Tbl1 VALUES('10002','CA','Tariff Request',2,'2011-01')INSERT INTO Tbl1 VALUES('10003','US','Consolidation',1,'2011-01')INSERT INTO Tbl1 VALUES('10003','US','Shipping Advise',3,'2011-01')INSERT INTO Tbl1 VALUES('10001','MX','Tariff Request',2,'2011-03')INSERT INTO Tbl1 VALUES('10002','CA','Consolidation',3,'2011-03')INSERT INTO Tbl1 VALUES('10004','US','Shipping Advise',2,'2011-02')INSERT INTO Tbl1 VALUES('10003','US','Tariff Request',5,'2011-02')INSERT INTO Tbl1 VALUES('10001','MX','Consolidation',2,'2011-02')INSERT INTO Tbl1 VALUES('10002','CA','Consolidation',1,'2011-02')DECLARE @Topic VARCHAR(2000)SELECT Customer, Country, Topic, SUM(CallCount) as CallCountFROM Tbl1WHERE Topic = @TopicGROUP BY Customer, Country, Topic1. If I wanted to pass in the value(s): 'Shipping Advise' and 'Consolidation' for the @topic variable. How would I do that. 2. How would I return all records when nothing is passed in. Can I set a default?Thanks for your help.