DescribeQuery (children 1)
 TableExpression (children 1)
  Subquery (children 1)
   SelectWithUnionQuery (children 1)
    ExpressionList (children 1)
     SelectQuery (children 2)
      ExpressionList (children 2)
       Identifier p.产品
       Identifier p.销量
      TablesInSelectQuery (children 2)
       TablesInSelectQueryElement (children 1)
        TableExpression (children 1)
         TableIdentifier test
       TablesInSelectQueryElement (children 1)
        ArrayJoin (children 1)
         ExpressionList (children 1)
          Identifier products (alias p)