Temporary Tables and Table Variables

全局临时表： ##T1

局部临时表： #T1

表变量： @T1

临时表 vs 表变量：可见性,持久性,性能（具体见下表）

临时表有统计信息可以支持优化

表变量不需要重新编译

 

Table 2-4: Comparison Summary

Functionality/Object Type	Local Temp Table	Table Variable	Table Expression
Scope/Visibility	Current and inner levels	Local Batch	Derived Table/CTE: Current statement View/Inline UDF: Global
Physical representation in tempdb	Yes	Yes	No
Part of outer transaction/Affected by outer transaction rollback	Yes	No	Yes
Logging	To support transaction rollback	To support statement rollback	Yes
Locking	Yes	No	Yes
Statistics/recompilations/efficient plans	Yes	No	Yes
Table size	Any	Typically recommended for small tables	Any