如何合並具有不同列號的兩個表？ MySQL的

Question

我想運行此查詢：

SELECT firstName , secondName , lastName 
   FROM
       (SELECT firstName,secondName,lastName FROM table1

        UNION

        SELECT firstName,NULL,NULL FROM table2

       )resutls

我想在第二個測試中添加兩個Null列，我該怎么做？

或重復兩次firstname->

SELECT firstName , secondName , lastName 
 FROM
   (SELECT firstName,secondName,lastName FROM table1

    UNION

    SELECT firstName,firstName,firstName FROM table2

   )resutls

我想在第二個選擇中再添加兩個cols，因為table2只有一個col（first name），如果我只選擇一個col，則聯合將不起作用。

Answer 1

您的查詢應為：

SELECT firstName , secondName , lastName 
 FROM
   (SELECT firstName,secondName,lastName FROM table1
    UNION
    SELECT firstName, NULL as secondName, NULL as lastName FROM table2
   ) resutls

使用列名的別名將其視為第二張表的新列。

這將為您工作。 :)

Answer 2

嘗試這個

SELECT firstName , secondName , lastName 
FROM
(SELECT firstName as fistname ,secondName as secondname ,lastName as lastname FROM table1

 UNION

 SELECT firstName as firstname,firstName as  '' ,firstName as '' FROM table2

 )

這將使您將列名設置為null