• Table variables (DECLARE @t TABLE) are visible only to the connection that creates it, and are deleted when the batch or stored procedure ends.

  • Local temporary tables (CREATE TABLE #t) are visible only to the connection that creates it, and are deleted when the connection is closed.

  • Global temporary tables (CREATE TABLE ##t) are visible to everyone, and are deleted when all connections that have referenced them have closed.

  • Tempdb permanent tables (USE tempdb CREATE TABLE t) are visible to everyone, and are deleted when the server is restarted.