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| Append | The append sub query takes the results of one query and appends them to another set of results as additional columns. The purpose of this query is to allow the result of one query to be compared to that of another. |
| Union | The union sub query combines the results of two queries into a single table of matching columns. Unions can be useful in a data warehouse application when tables aren't perfectly normalised. |
| Minus | The minus sub query takes distinct rows of one query and returns the rows that don't appear in the second query. |
| Intersect | The intersect query takes the results of two queries and returns only the rows that appear in both sets. |
Enabling Sub Queries
- To create a new sub query tick the sub query check box in the analysis section of the report options menu. This will provide a + Sub Query Menu link at the top of the report data section.
- Choose the query type you wish to create. On selection a new tab will be displayed (Sub Query). This will enable you to create your new sub query.
Sub Query Relation to Master Query
When creating a sub query the data that is returned needs to be related to the initial or Master query. The sub query cannot run independent of the master query. So the implications is that for each type of sub query different join rules exist to link the sub queries results sets with those of the master query.
Changing the Sub Query tab display name
Initially the display name of a sub query is "Sub Query" . However by clicking to the report options menu for the sub query you can change the display name to something more meaningful if required.
Append Queries
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