A special data type that can be used to store a result set for later processing. Its primary use is for temporary storage of a set of rows, which are to be returned as the result set of a table-valued function.
Functions and variables can be declared to be of type table. table variables can be used in functions, stored procedures, and batches.
Use table variables instead of temporary tables, whenever possible. table variables provide the following benefits:
* A table variable behaves like a local variable. It has a well-defined scope, which is the function, stored procedure, or batch in which it is declared.
Within its scope, a table variable may be used like a regular table. It may be applied anywhere a table or table expression is used in SELECT, INSERT, UPDATE, and DELETE statements. However, table may not be used in the following statements:
INSERT INTO table_variable EXEC stored_procedure
SELECT select_list INTO table_variable statements.
table variables are cleaned up automatically at the end of the function, stored procedure, or batch in which they are defined.
* CHECK constraints, DEFAULT values and computed columns in the table type declaration cannot call user-defined functions.
* table variables used in stored procedures result in fewer recompilations of the stored procedures than when temporary tables are used.
* Transactions involving table variables last only for the duration of an update on the table variable. Thus, table variables require less locking and logging resources.
Assignment operation between table variables is not supported. In addition, because table variables have limited scope and are not part of the persistent database, they are not impacted by transaction rollbacks.