SQL不同表

Question

獲取值我得到了2 SQL表所示：

user_logs 
-id 
-log_date 
-log 

system_logs 
-id 
-create_date 
-log 

它是更多鈔票從這些表中獲取值，並按日期排序呢？

Answer 1

您正在尋找這樣的事情查詢

(select id, date, log from user_logs) 
union 
(select id, date, log from system_logs) 
order by date; 

更好的設計可能是使用一個表中的列編號，日期，日誌和log_type其中log_type定義日誌是否是一個用戶或系統日誌。

Answer 2

SELECT id, date FROM user_logs UNION SELECT id, date from system_logs ORDER BY date DESC; 

或者類似的東西，無論如何UNION是你正在尋找的關鍵字，see link。

Answer 3

使用UNION

SELECT * 
FROM 
(
    SELECT id, date, log FROM user_logs 
    UNION 
    SELECT id, date, log FROM system_logs 
) 
ORDER BY date desc 

Answer 4

SELECT * 
FROM 
(SELECT id, 
      date, 
      log 
    FROM system_logs 

    UNION 

    SELECT id, 
      date, 
      log 
    FROM user_logs) order by date DESC 

OR

SELECT id, 
       date, 
       log 
     FROM system_logs 

     UNION 

     SELECT id, 
       date, 
       log 
     FROM user_logs order by date DESC