Union queries

In AX 2009 a great enhancement was introduced to the queries – support for union operation was added. A new property was added to the AOT queries – QueryType. It has two values:

• Join – regular query


• Union – union query

In the case of union query several datasources of the same type (the same table) can be placed on the query datasource root node. Note, that all datasources except the first one will have a property called UnionType, which specifies what should be done with duplicated records that may appear because of union:

• Union – remove duplicated records


• UnionAll – keep duplicated records

Additional datasources can be added to the deeper levels of the query under any datasource that participates in union. Those will be translated into joins. The only allowed join types for the union query are exists and notexists join.