Explain EXPLAIN QUERY TREE (children 2)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 4)
    ExpressionList (children 1)
     Asterisk
    TablesInSelectQuery (children 2)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier t1
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       TableIdentifier t2
      TableJoin (children 1)
       Function equals (children 1)
        ExpressionList (children 2)
         Identifier t1.id
         Identifier t2.id
    ExpressionList (children 2)
     OrderByElement (children 1)
      Identifier t1.id
     OrderByElement (children 1)
      Identifier t2.id
    Set
