Should I use temp table or table variable?

If you will be deleting or updating a large number of rows then the temp table may well perform much better than a table variable – if it is able to use rowset sharing (see “Effects of rowset sharing” below for an example). If the optimal plan using the table will vary dependent on data then use a #temporary table.

Is table variable faster than temp table?

Whereas, a Temporary table (#temp) is created in the tempdb database. So table variable is faster then temporary table. ⇒ Temporary tables are allowed CREATE INDEXes whereas, Table variables aren’t allowed CREATE INDEX instead they can have index by using Primary Key or Unique Constraint.

What is difference between CTE and table variable?

CTE is a named temporary result set which is used to manipulate the complex sub-queries data. You cannot create an index on CTE. Table Variable acts like a variable and exists for a particular batch of query execution. It gets dropped once it comes out of a batch.

How do you use table variables?

To declare a table variable, start the DECLARE statement. The name of table variable must start with at(@) sign. The TABLE keyword defines that used variable is a table variable. After the TABLE keyword, define column names and datatypes of the table variable in SQL Server.

Do table variables use tempdb?

Table variables are created in the tempdb database similar to temporary tables. If memory is available, both table variables and temporary tables are created and processed while in memory (data cache).

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.

How do you declare a table variable?

To declare a table variable, you use the DECLARE statement as follows:

1. DECLARE @table_variable_name TABLE ( column_list );
2. DECLARE @product_table TABLE ( product_name VARCHAR(MAX) NOT NULL, brand_id INT NOT NULL, list_price DEC(11,2) NOT NULL );

How do you drop a table variable in SQL?

We cannot drop a table variable using an explicit drop statement. It is stored in the tempdb system database. The storage for the table variable is also in the tempdb database. We can use temporary tables in explicit transactions as well….We use the following format for defining a temporary table:

1. Define.
2. Use.
3. Drop.

How to improve the performance of table variables in SQL Server?

With large data, the performance improvement can be significant, from tens of minutes to seconds. Now, the server compiles its code before running each query and does not use the execution plan from the cache, but generates a new one, depending on the amount of data in the variable, and this usually helps a lot.

How to optimize temp table and table variables?

If you use temporary tables, table variables, or table-valued parameters, consider conversions of them to leverage memory-optimized tables and table variables to improve performance. The code changes are usually minimal. Scenarios which argue in favor of conversion to In-Memory. Technical steps for implementing the conversions to In-Memory.

Why are table variables bad for SQL Server?

Batches or store procedures that execute join operations on table variables may experience performance problems if the table variable contains a large number of rows. Table variable were introduced in SQL Server with the intention to reduce recompiles, however if they are used in batches or store procedures they may cause a performance issue.

Why does the table variable outperform the temporary table?

When deleting rows based on the primary key the table variable outperforms the temporary table. As with the SQL Profiler results of the INSERT statement this is probably due to the fact that an extra index has to be updated.