Explain EXPLAIN (children 2)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 3)
    ExpressionList (children 1)
     Asterisk
    TablesInSelectQuery (children 2)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier users (alias u1)
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       Subquery (alias u2) (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 1)
          SelectQuery (children 3)
           ExpressionList (children 2)
            Function CAST (alias age_sum) (children 1)
             ExpressionList (children 2)
              Function sum (children 1)
               ExpressionList (children 1)
                Identifier age
              Literal \'Nullable(Int64)\'
            Identifier name
           TablesInSelectQuery (children 1)
            TablesInSelectQueryElement (children 1)
             TableExpression (children 1)
              TableIdentifier users
           ExpressionList (children 1)
            Identifier name
      TableJoin (children 1)
       Function equals (children 1)
        ExpressionList (children 2)
         Identifier u1.name
         Identifier u2.name
    Function less (children 1)
     ExpressionList (children 2)
      Identifier uid
      Identifier age_sum
