To Check How May Connections are open in your Sql Server..

SELECT      DB_NAME(dbid) as DBName,      COUNT(dbid) as NumberOfConnections,     loginame as LoginName FROM     sys.sysprocesses WHERE      dbid > 0 GROUP BY      dbid, loginame

Implement Data Integrity in Sql Server

create table (TabelName)(

 RegNo int constraint pkey primary key,

 StuID int unique,

 SName char (20),

 sAge int constraint chage check (sage between 15 and 25),

 sCity char(20)check(scity in ('jaipur','kota')),

 sphone char (12)check (sphone like '[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]'),

 sstate char (20) default 'Rajasthan'

 )

Select * from (TableName)