The SessionID property returns the session identifier (session ID), a unique identifier that is generated by the server when the session is created. The session ID is returned as a LONG data type.
You should not use the SessionID property to generate primary key values for a database application. This is because if the Web server is restarted, some SessionID values may be the same as those generated before the server was stopped. Instead, you should use an auto-increment column data type, such as IDENTITY with Microsoft® SQL Server™ or COUNTER with Microsoft Access.