how to create a Cursor in sql server

To create a cursor in sql server

DECLARE @uid VARCHAR(500)
DECLARE @AgtName VARCHAR(500)

DECLARE curSample SCROLL CURSOR
FOR
SELECT UserID,AgentName FROM TestTable
OPEN curSample
FETCH NEXT FROM curSample INTO @uid,@AgtName

WHILE (@@FETCH_STATUS <> -1)
BEGIN

Update TestTable SET UserID='Test' WHERE UserID = @uid

FETCH NEXT FROM curSample INTO @uid,@AgtName
END

CLOSE curSample
DEALLOCATE curSample