Temporary Tables VS Table Variables

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I was having a good discussion with a fellow developer around SQL Server Temporary Tables and Table Variables. Here are some points from the discussion:

Temporary tables are like regular tables but stored in the tempdb database. These tables get dropped after they have been used. Temporary tables are of two types,

Local Temporary table - defined using a pound sign (#) and accessible only within the session that created it

Global Temporary table - defined using double pound signs (##) and visible to all users.

Table Variables is a data type that looks similar to a table but has a tighter lifetime scope (i.e within a function, stored procedure or batch that it is declared in) and should be used with small datasets.

Here are some differences between Temporary Table and Table Variables

Temporary Tables	Table Variables
Created and stored in tempdb database	Created in Memory (although it can write to tempdb)
Transaction logs are recorded for temporary tables	Transaction logs are not recorded for the table variables
They are bound to transactions.	They are not bound to any transactions. So no effect of transaction rollbacks
Can participate in parallel operations	Cannot participate in parallel operations
The log activity remains till it is manually cleared or the server restarts	Table variable log activity is truncated immediately
SQL Server creates statistics for temporary tables	SQL Server does not create statistics for table variables
Stored procedure containing temporary tables cannot be pre-compiled	Stored procedures containing table variables can be pre-compiled
You can drop a Temporary Table	You cannot manually drop a table variable
You can create indexes on them	You cannot ‘explicitly’ create Indexes on them (exception is the index created while creating a Primary Key)

For further reading, http://databases.aspfaq.com/database/should-i-use-a-temp-table-or-a-table-variable.html and Table Variables

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About The Author

Suprotim Agarwal, ASP.NET Architecture MVP works as an Architect Consultant and provides consultancy on how to design and develop Web applications.

Suprotim is also the founder and primary contributor to DevCurry, DotNetCurry and SQLServerCurry. He has also written an EBook 51 Recipes using jQuery with ASP.NET Controls.

Follow him on twitter @suprotimagarwal

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