4> IF OBJECT_ID('dbo.Sessions') IS NOT NULL
5> DROP TABLE dbo.Sessions;
6> GO
1>
2> CREATE TABLE dbo.Sessions
3> (
4> keycol INT NOT NULL IDENTITY PRIMARY KEY,
5> app VARCHAR(10) NOT NULL,
6> usr VARCHAR(10) NOT NULL,
7> starttime DATETIME NOT NULL,
8> endtime DATETIME NOT NULL,
9> CHECK(endtime > starttime)
10> );
11> GO
1>
2> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app1', 'user1', '20060212 08:30', '20060212 10:30');
3> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app1', 'user2', '20060212 08:30', '20060212 08:45');
4> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app1', 'user1', '20060212 09:00', '20060212 09:30');
5> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app1', 'user2', '20060212 09:15', '20060212 10:30');
6> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app1', 'user1', '20060212 09:15', '20060212 09:30');
7> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app1', 'user2', '20060212 10:30', '20060212 14:30');
8> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app1', 'user1', '20060212 10:45', '20060212 11:30');
9> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app1', 'user2', '20060212 11:00', '20060212 12:30');
10> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app2', 'user1', '20060212 08:30', '20060212 08:45');
11> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app2', 'user2', '20060212 09:00', '20060212 09:30');
12> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app2', 'user1', '20060212 11:45', '20060212 12:00');
13> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app2', 'user2', '20060212 12:30', '20060212 14:00');
14> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app2', 'user1', '20060212 12:45', '20060212 13:30');
15> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app2', 'user2', '20060212 13:00', '20060212 14:00');
16> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app2', 'user1', '20060212 14:00', '20060212 16:30');
17> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES('app2', 'user2', '20060212 15:30', '20060212 17:00');
18> GO
1>
2> SELECT app, MAX(cnt) AS mx
3> FROM (SELECT app,
4> (SELECT COUNT(*) FROM dbo.Sessions AS C
5> WHERE ts >= starttime
6> AND ts < endtime) AS cnt
7> FROM (SELECT DISTINCT app, starttime AS ts
8> FROM dbo.Sessions) AS T) AS D
9> GROUP BY app;
10> GO
app mx
---------- -----------
app1 5
app2 4
1>
2> drop table sessions;
3> GO
1>
2>