Explain EXPLAIN (children 2)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 2)
    ExpressionList (children 1)
     Function avgWeighted (children 1)
      ExpressionList (children 2)
       Identifier x
       Identifier y
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       Subquery (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 2)
          SelectQuery (children 1)
           ExpressionList (children 3)
            Literal NULL
            Literal UInt64_255 (alias x)
            Literal UInt64_1 (alias y)
          SelectQuery (children 1)
           ExpressionList (children 3)
            Identifier y
            Literal NULL (alias x)
            Literal UInt64_1 (alias y)
