Explain EXPLAIN SYNTAX (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 3)
    ExpressionList (children 2)
     Identifier number
     Identifier square_number
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       Subquery (alias squares) (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 1)
          SelectQuery (children 3)
           ExpressionList (children 1)
            Function multiply (alias square_number) (children 1)
             ExpressionList (children 2)
              Identifier number
              Literal UInt64_2
           ExpressionList (children 2)
            Identifier number
            Identifier square_number
           TablesInSelectQuery (children 1)
            TablesInSelectQueryElement (children 1)
             TableExpression (children 1)
              TableIdentifier numbers_indexed
    Function equals (children 1)
     ExpressionList (children 2)
      Identifier number
      Literal UInt64_999
