dpb_4431 2017-08-07 02:25
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从左连接返回mysql查询中的最后一行

I am trying to get the last row of table2 that I left join with table1.

Table1 column:

  1. id
  2. name
  3. created date

Table2 column:

  1. id
  2. last_login
  3. ip_address

Login data stored into table2 everytime user logged in. So I am trying to display all users from table1 which is displaying the last_login record from table2.

Here is my current query :

SELECT table1.*, table2.last_login
FROM table1
LEFT JOIN table2 ON table2.id= table1.id
ORDER BY table2.last_login desc;

With the query above I am able to get all the data from both table, where if user A logged 5 times, the query will return 5 rows, but I wanted to only showing the user details and their last_login data. If I add GROUP BY table1.id it return 1 row record for every user but the last_login data is not showing the latest record.

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2条回答 默认 最新

  • dongtu1789 2017-08-07 02:32
    关注

    If you just want the last login, perhaps a correlated subquery would do:

    SELECT t1.*,
           (SELECT MAX(t2.last_login)
            FROM table2 t2
            WHERE t2.id = t1.id
           ) as last_login
    FROM table1 t1
    ORDER BY last_login desc;
    

    For performance, you want an index on table2(id, last_login).

    本回答被题主选为最佳回答 , 对您是否有帮助呢?
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