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