Reset Identity Seed after deleting records in SQL Server

DBCC CHECKIDENT ('YourTableName', RESEED, 1)
Go
Also maybe you need shrink your table
ALTER INDEX PK_yourIndexName ON YourTableName REBUILD
Also maybe you need duplicate your records on table
DECLARE @intFlag INT
SET @intFlag = 1
WHILE (@intFlag <=21)
BEGIN
INSERT INTO yourTableName SELECT TOP 1
field1,
field2,
field3,
...
FROM yourTableName
SET @intFlag = @intFlag + 1
END

SQL SERVER – Simple Example of WHILE Loop With CONTINUE and BREAK Keywords

1) Example of WHILE Loop
DECLARE @intFlag INT
SET 
@intFlag 1
WHILE (@intFlag <=5)
BEGIN
PRINT 
@intFlag
SET @intFlag @intFlag 1
END
GO

ResultSet:
1
2
3
4
5

2) Example of WHILE Loop with BREAK keyword
DECLARE @intFlag INT
SET 
@intFlag 1
WHILE (@intFlag <=5)
BEGIN
PRINT 
@intFlag
SET @intFlag @intFlag 1
IF @intFlag 4
BREAK;
END
GO

ResultSet:
1
2
3

3) Example of WHILE Loop with CONTINUE and BREAK keywords
DECLARE @intFlag INT
SET 
@intFlag 1
WHILE (@intFlag <=5)
BEGIN
PRINT 
@intFlag
SET @intFlag @intFlag 1
CONTINUE;
IF @intFlag -- This will never executed
BREAK;
END
GO

ResultSet:
1
2
3
4
5

http://blog.sqlauthority.com/2007/10/24/sql-server-simple-example-of-while-loop-with-continue-and-break-keywords/