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Temp Variables

SQL Server TSQL Table Variables

Table Variables In SQL Server: These tables behave very much like other variables in their scoping rules. They are created when they are declared and are dropped when they go out of scope. They cannot be explicitly dropped. Like with temp tables, table variables also reside in TempDB. They are also generally accessed only from memory, unless the server is under memory pressure or the amount of data in the table is large.

Table variables can have a primary key, but no indexes can be created on them. They don’t have any statistics maintained on the columns. This makes table variables less optimal for large numbers of rows, as the optimizer has no way of … Read the rest

SQL Server TSQL Temporary Table

Temp tables in SQL Server: they are just like any normal tables except that they are created in the TempDB database. They persist until dropped, or until the connection that created them disappears. They are visible in the procedure that created them and any procedures that it calls. Just like normal tables and have primary keys, constraints, indexes and column statistics which are kept for the table which makes query execution really fast in most cases. Temp tables can be created in all versions of SQL Server including SQL Server Express Edition.

Temp tables have space assigned to them in the TempDB database and are generally accessed only from memory, unless the server is under memory pressure or the amount … Read the rest

CTE vs Temp Table vs Temp variables

Temp tables: they are just like any normal tables except that they are created in the TempDB database. They persist until dropped, or until the connection that created them disappears. They are visible in the procedure that created them and any procedures that it calls. Just like normal tables and have primary keys, constraints, indexes and column statistics which are kept for the table which makes query execution really fast in most cases.

Temp tables have space assigned to them in the TempDB database and are generally accessed only from memory, unless the server is under memory pressure or the amount of data in the table is large.

Table Variables: These tables behave very much like other variables in their … Read the rest

Temporary Variables vs Temporary Tables SQL Server 2008/2005

Myth: A table variable is a memory-only structure.
This is not True. A Temp table variable might hold more data than can fit in memory, it has to have a place on disk to store data. Table variables are created in the tempdb database similar to temporary tables.

Note: If memory is available, both table variables and temporary tables are created and processed while in memory (data cache).

Normally whether to go with Temp Variables or Temp Tables depends on:
•The number of rows that are inserted to the table.
•The number of recompilations the query is saved from.
•The type of queries and their dependency on indexes and statistics for performance.
Some other important advantages of temporary tables:
•Non-clustered … Read the rest