在表已被锁定的情况下执行嵌套SQL时，“表未被锁定表锁定”

Question

我试图执行以下sql，由于多个进程之间的同步，我首先锁定了表

lock tables Report write;
SELECT id,taskTime,timeout,maxExecutionTimes,currentOwner, tenantID, 
case when tenantID = 'NoValue' then 1 else 0 end tenantOrder, 
case when tenantID in (select distinct tenantID from Report where state = 2) then 1 else 0 end mspInHandling 
FROM Report WHERE state=2 and maxExecutionTimes>executionTimes  
order by tenantOrder desc, mspInHandling limit 1

虽然表已被锁定，但是此sql语句始终给我一个错误，例如：“表报表未被锁定表锁定”

如果我不锁定表，则SQL语句可以很好地运行，我认为这可能与嵌套（select distinct tenantID from Report where state = 2）有关，但找不到出路。

有人可以帮忙吗？预先感谢。

Answer 1

使用子查询时，需要给子查询表加上别名，并使用相同的别名锁定该表。您可以尝试一下吗？：

lock tables Report write, Report as r2 read;
SELECT id,taskTime,timeout,maxExecutionTimes,currentOwner, tenantID, 
case when tenantID = 'NoValue' then 1 else 0 end tenantOrder, 
case when tenantID in (select distinct tenantID from Report as r2 where state = 2) then 1 else 0 end mspInHandling 
FROM Report WHERE state=2 and maxExecutionTimes>executionTimes  
order by tenantOrder desc, mspInHandling limit 1

在上述sql中，我锁定表Report as r2 read并为子查询Report as r2加上别名

reference