何时在本地临时表上使用SSIS中的全局临时表？

Question

When to use global Temp table in SSIS over Local temp table ? I know the difference in terms of SQL usage but when it comes to implement in SSIS which one to prefer in which scenario ?

Answer 1

Little theory recap for MS SQL temp tables:

• Global temp table - you create it, fill/select, delete it. Table remains in TempDB and is deleted when all users that are referencing the table disconnect from the instance of SQL Server. Table is accessible by other connections/sessions.
• Local temp table - you create it and can use within your connection session. Table is dropped automatically when you close connection session.

So if you need to store something just for your scope, Local tables are better, since it is deleted automatically as you close the session. Global tables are better if you need to pass data between sessions/processes. Drawback of Global Temp tables - you have to ensure it does not exist when you create it, drop when you are done etc.

Regarding temp tables and SSIS. SSIS usually opens a new connection for each operation with DB - Execute SQL Task. In data flow, it opens a new connection for each component . Therefore, local Temp table will be accessible only in one Task/Data Flow component. In such session pattern you have the following options:

• Use Local temp tables within one command of Execute SQL task. Another task means another connection, local temp tables are dropped.
• Use Global temp tables and check table existence when creating, delete table afterwards etc.
• Use Local temp tables and set RetainSameConnection=true property of related Connection Manager. This setting means that SSIS does not drop connection after execution of Execute SQL task. In some cases SSIS still might open another connection. More details how to use it - see similar question .