Mysql從UNION ALL查詢結果集中查詢對應列出現錯誤"Every derived table must have its own alias"

在使用UNION ALL聯合表的時候出現了出現了Every derived table must have its own alias 錯誤

sql如下：

SELECT * FROM 
    (SELECT 1 CorpLevel,t.Operator_Id CorpId,t.Operator_Name CorpName,'1' CorpType FROM Fd_Operator t
         UNION ALL
     SELECT 2 CorpLevel,t.Con_Id CorpId,t.Con_Name CorpName,'2' CorpType FROM Fd_Consignor t
         UNION ALL
     SELECT 2 CorpLevel,t.Carrier_Id CorpId,t.Carrier_Name CorpName,'3' CorpType FROM Fd_Carrier t
         UNION ALL
     SELECT 3 CorpLevel,t.Ssa_Id CorpId,t.Ssa_Name CorpName,'4' CorpType FROM Fd_SupplySalesagency t) 
 WHERE CorpId='129'

出現如下錯誤：

1 queries executed, 0 success, 1 errors, 0 warnings

查詢：select * from (select 1 CorpLevel,t.Operator_Id CorpId,t.Operator_Name CorpName,'1' CorpType from Fd_Operator t union all select...

錯誤代碼： 1248
Every derived table must have its own alias

執行耗時   : 0 sec
傳送時間   : 0 sec
總耗時      : 0.001 sec 

錯誤信息解析：

Every derived table must have its own alias
每個派生表必須有自己的別名

修改後的sql：

SELECT * FROM 
    (SELECT 1 CorpLevel,t.Operator_Id CorpId,t.Operator_Name CorpName,'1' CorpType FROM Fd_Operator t
         UNION ALL
     SELECT 2 CorpLevel,t.Con_Id CorpId,t.Con_Name CorpName,'2' CorpType FROM Fd_Consignor t
         UNION ALL
     SELECT 2 CorpLevel,t.Carrier_Id CorpId,t.Carrier_Name CorpName,'3' CorpType FROM Fd_Carrier t
         UNION ALL
     SELECT 3 CorpLevel,t.Ssa_Id CorpId,t.Ssa_Name CorpName,'4' CorpType FROM Fd_SupplySalesagency t) 
 AS a WHERE a.CorpId='129'