Quick Answer: What Is The Difference Between Temp Table And Table Variable?

Are temp tables faster than table variables?

Summary of Performance Testing for SQL Server Temp Tables vs.

Table Variables.

As we can see from the results above a temporary table generally provides better performance than a table variable.

The only time this is not the case is when doing an INSERT and a few types of DELETE conditions..

What is a table variable?

Definition. The table variable is a special type of the local variable that helps to store data temporarily, similar to the temp table in SQL Server. In fact, the table variable provides all the properties of the local variable, but the local variables have some limitations, unlike temp or regular tables.

Which is faster CTE or temp table?

If you are joining multiple tables with millions of rows of records in each, CTE will perform significantly worse than temporary tables. Temp tables are always on disk – so as long as your CTE can be held in memory, it would most likely be faster (like a table variable, too).

Can you create an index on a CTE?

No. A CTE is a temporary, “inline” view – you cannot add an index to such a construct. If you need an index, create a regular view with the SELECT of your CTE, and make it an indexed view (by adding a clustered index to the view).

When would you use a temp table?

The best time to use temporary tables are when you need to store information within SQL server for use over a number of SQL transactions. Like a normal table, you’ll create it, interact with it (insert/update/delete) and when you are done, you’ll drop it. There are two differences between a table and a temporary table.

Are temp tables dropped automatically?

Temp tables are automatically dropped as soon as they go out of scope (the proc that they were created in completes) or the connection that created them closes.

How do you declare a table variable?

To declare a table variable, you use the DECLARE statement as follows: DECLARE @table_variable_name TABLE ( column_list ); In this syntax, you specify the name of the table variable between the DECLARE and TABLE keywords. The name of the table variables must start with the @ symbol.

Can we join table with table variable?

f you are using a table variable in a join, you will need to alias the table in order to execute the query. You can use a table variable with dynamic SQL, but you must declare the table inside the dynamic SQL itself.

Which is better table variable or temp table?

A temp table can have indexes, whereas a table variable can only have a primary index. If speed is an issue Table variables can be faster, but obviously if there are a lot of records, or the need to search the temp table of a clustered index, then a Temp Table would be better.

Can we use table variable in view?

There is certainly a good reason for views not supporting table variables. Table variables are only visible in the batch they are created in, and the CREATE VIEW statement must be in a batch of its own, so the table variable never exist when the CREATE VIEW statement runs.

Is CTE a temp table?

CTE stands for Common Table Expressions. It was introduced with SQL Server 2005. It is a temporary result set and typically it may be a result of complex sub-query. Unlike the temporary table, its life is limited to the current query.

Why drop table if exists?

The DROP TABLE SQL statement enables you to delete a table from the database. If the table did not exist then attempting to DROP it would cause an error to occur. The DROP TABLE IF EXISTS SQL statement enables a check to see that the table exists prior to attempting the dropping (deletion) of the table.

Can we create temp table in view?

You cannot create or drop tables in a view. … CTEs are temporary result sets that are defined within the execution scope of a single statement and they can be used in views.

Do Table variables use tempdb?

Table variables use tempdb similar to how temporary tables use tempdb. Table variables are not in-memory constructs but can become them if you use memory optimized user defined table types.

Does using temp tables improve performance?

Temporary Tables are considered as regular database object, in terms of transaction handling and performance, therefore using many temporary tables in your stored procedures can lead to very poor database performance.

What is difference between temp and table variable?

A Temp table is easy to create and back up data. Table variable involves the effort when you usually create the normal tables. Temp table result can be used by multiple users.

Are CTEs faster than subqueries?

The performance of CTEs and subqueries should, in theory, be the same since both provide the same information to the query optimizer. One difference is that a CTE used more than once could be easily identified and calculated once. The results could then be stored and read multiple times.

Can I pass table variable to stored procedure?

Table-valued parameters are declared by using user-defined table types. You can use table-valued parameters to send multiple rows of data to a Transact-SQL statement or a routine, such as a stored procedure or function, without creating a temporary table or many parameters.

Can you have a foreign key on a temp table?

One of the restrictions on a foreign key relationship is that you cannot delete a row from a key table that is depended upon by your temp table. … Could be because you can’t have cross-database foreign key constraints and temp tables technically are created in the TempDB database.

Can I declare variable in view?

You can’t declare variables in a view. … Edit – you might also be able to put something into a CTE and keep it as a view. e.g.

Can table variables have INDEXes?

In SQL Server 2000 – 2012 indexes on table variables can only be created implicitly by creating a UNIQUE or PRIMARY KEY constraint. The difference between these constraint types are that the primary key must be on non nullable column(s). … Also a table can only have one primary key but multiple unique constraints.