Explain EXPLAIN (children 2)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 2)
    ExpressionList (children 4)
     Identifier lhs.id
     Identifier lhs.value_1
     Identifier rhs.id
     Identifier rhs.value_1
    TablesInSelectQuery (children 2)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier test_table_1 (alias lhs)
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       TableIdentifier test_table_2 (alias rhs)
      TableJoin (children 1)
       Function equals (children 1)
        ExpressionList (children 2)
         Identifier lhs.id
         Identifier rhs.id
