Temporary tables in SQL Server

Introduction

Temporary tables are a useful tool in SQL Server provided to allow for short term use of data. There are two types of temporary table in SQL Server, local and global.

Local temporary tables are only available to the current connection to the database for the current user and are dropped when the connection is closed. Global temporary tables are available to any connection once created, and are dropped when the last connection using it is closed.

Both types of temporary tables are created in the system database tempdb.

Creating Temporary Tables

Temporary tables can be created like any table in SQL Server with a CREATE TABLE or SELECT..INTO statement. To make the table a local temporary table, you simply prefix the name with a (#). To make the table a global temporary table, prefix it with (##).

Example
-- Create a local temporary table
CREATE TABLE #LocalTempTable
(
Field1 INT,
Field2 VARCHAR(20)
)

CREATE TABLE ##GlobalTempTable
(
Field1 INT,
Field2 VARCHAR(20)
)
* you can do all the DML operation on Temporary table.