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)
       Subquery (alias s) (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 1)
          SelectQuery (children 2)
           ExpressionList (children 1)
            Function plus (alias key) (children 1)
             ExpressionList (children 2)
              Identifier number
              Literal UInt64_2
           TablesInSelectQuery (children 1)
            TablesInSelectQueryElement (children 1)
             TableExpression (children 1)
              Function numbers (children 1)
               ExpressionList (children 1)
                Literal UInt64_4
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       TableIdentifier test (alias t)
      TableJoin (children 1)
       ExpressionList (children 1)
        Identifier key
    ExpressionList (children 2)
     OrderByElement (children 1)
      Identifier s.key
     OrderByElement (children 1)
      Identifier t.key
    Set
