A query could contain some union’ed queries. This is similar to the sql usage, but limited in some way.
- Sort Order
SELECT * FROM ( QUERY_B UNION QUERY_C ) QUERY_A
If a condition is set, the union query will be encapsulated and the condition is added with where.
SELECT * FROM ( SELECT * FROM (QUERY_B) WHERE CONDITION_B UNION SELECT * FROM (QUERY_C) WHERE CONDITION_C ) QUERY_A