QuerySelect

Each query is composed of one or more select statements:

Field or Control	Description
Main Select	The instance of the first SELECT statement of the Query is the Main Select. There can only be one Main Select statement in the Query. This instance consists of the QueryOutputFIelds, QueryCriteria, and the QueryExpressions for the Main Select statement.
Union	In addition to the Main Select, a query can have one or more unions. The Unions are added by using the AddUnion method.
Sub-Select	A subquery used in the criteria of the Main Select or in a Union.