将 2 个 select 语句转换为 MySql 中的单个语句

Question

我使用两个子查询从同一个表中获取log_msg和log_state 。 我想问一下如何将这 2 个子查询转换为单个子查询，以便我不需要两次调用同一个表。

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过滤每个组的顶部日志记录：

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)