將 2 個 select 語句轉換為 MySql 中的單個語句

Question

我使用兩個子查詢從同一個表中獲取log_msg和log_state 。 我想問一下如何將這 2 個子查詢轉換為單個子查詢，以便我不需要兩次調用同一個表。

SELECT t1.objectId, t1.name, 
(SELECT a.logs FROM logTable a WHERE a.logId = t1.logId ORDER BY id DESC LIMIT 1) AS log_msg,
(SELECT a.state FROM logTable a WHERE a.logId = t1.logId ORDER BY id DESC LIMIT 1) AS log_state,
FROM table1 t1 WHERE t1.CreateDate >= '2019-12-01';

Answer 1

您可以按如下方式加入和過濾每個組的頂部日志記錄：

select t1.objectId, t1.name, l.logs, l.state
from table1 t1
inner join logTable l
    on l.id = (select max(l1.id) from logTable l1 where l1.logId = t1.id)