Different Types of Temporary Tables

Different Types of Temporary Tables

SQL Server provides two types of temp tables based on the Scope and Behavior of the table.

• Local Temp Table
• Global Temp Table

Local Temp Table

Local temp tables are only available to the current connection for the user; and they are automatically deleted when the user disconnects from instances. Local temporary table name is stared with ("#") sign.

Global Temp Table

Global Temporary tables name starts with  ("##"). Once this table has been created by a connection, like a permanent table it is then available to any user by any connection. It can only be deleted once all connections have been closed.

Creating Temporary Table in SQL Server 2008

As I have already discussed, there are two types of temporary tables available. Here I am going to describe each of them.

Local Temporary Table

The syntax given below is used to create a local Temp table in SQL Server 2008:

CREATE TABLE #LocalTmpTable(
UserID int,
UserName varchar(50), 
UserAddress varchar(150))

The above script will create a temporary table in tempdb database. We can insert or delete records in the temporary table similar to a general table like:

insert into #LocalTmpTable values ( 1, 'Dhirendra','Noida');

Now select records from that table:

select * from #LocalTmpTable

After execution of all these statements, if you close the query window and again execute "Insert" or "Select" Command, it will throw the following error:

Msg 208, Level 16, State 0, Line 1
Invalid object name '#LocalTmpTable'.

This is because the scope of Local Temporary table is only bounded with the current connection of current user.

Global Temporary Table

The scope of Global temporary table is the same for the entire user for a particular connection. We need to put "##" with the name of Global temporary tables. Below is the syntax for creating a Global Temporary Table: 

CREATE TABLE ##NewGlobalTmpTable(
UserID int,
UserName varchar(50), 
UserAddress varchar(150))

The above script will create a temporary table in tempdb database. We can insert or delete records in the temporary table similar to a general table like:

insert into ##NewGlobalTmpTable values ( 1, 'Dhirendra','Noida');

Now select records from Globle temp table:

select * from ##NewGlobalTmpTable