Listing 1: Creating and Populating the Calls Table

CREATE TABLE Calls
(
  username VARCHAR(32)   NOT NULL,
  calldate SMALLDATETIME NOT NULL, -- start call date/time
  duration INT           NOT NULL, -- in minutes
  PRIMARY KEY(username, calldate)
)

INSERT INTO Calls VALUES('user1', '20030212 21:30', 60)   -- 1 hour
INSERT INTO Calls VALUES('user2', '20030212 23:00', 1440) -- 24 hours
INSERT INTO Calls VALUES('user3', '20030204 23:00', 4320) -- 72 hours