Explain EXPLAIN (children 2)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 4)
    ExpressionList (children 1)
     Asterisk
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       Subquery (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 1)
          SelectQuery (children 2)
           ExpressionList (children 1)
            Asterisk
           TablesInSelectQuery (children 2)
            TablesInSelectQueryElement (children 1)
             TableExpression (children 1)
              TableIdentifier users (alias u1)
            TablesInSelectQueryElement (children 2)
             TableExpression (children 1)
              TableIdentifier users (alias u2)
             TableJoin (children 1)
              Literal UInt64_1
    Function equals (children 1)
     ExpressionList (children 2)
      Identifier age
      Identifier u2.age
    ExpressionList (children 1)
     OrderByElement (children 1)
      Identifier ALL
