group by查詢每組時間最新的一條記錄

最近需要查詢每組時間最新的記錄

表如下：

目標結果是：

 

 

一開始的想法：

select * from

 

(select * from log where account_id = 45 order by shop_id,create_time desc)  w

 

group by w.shop_id

 

這種寫法看着沒毛病，但是查詢出來不是每組最新的一條

 

 

正確的寫法很多這里說個認為比較簡單的

select * from log where id in

 

(select SUBSTRING_INDEX(GROUP_CONCAT(id order by create_time desc), ',', 1)   from log where account_id = 45 group by shop_id)

 

分部解讀：

根據條件查詢出分組的所有按時間降序的記錄id並拼接

1.select GROUP_CONCAT(id order by create_time desc) from log where account_id = 45 group by shop_id

 

 

2. 查詢每個分組中時間最新的那條記錄的id

select SUBSTRING_INDEX(GROUP_CONCAT(id order by create_time desc), ',', 1)   from log where account_id = 45 group by shop_id

 

3.

select * from log where id in

 

(select SUBSTRING_INDEX(GROUP_CONCAT(id order by create_time desc), ',', 1)   from log where account_id = 45 group by shop_id)