You have a MySQL replication setup and you intentionally stop the SQL thread on the slave.
#你有一个MySQL复制设置，并且有意停止从机上的SQL线程；
mysql>SHOW SLAVE STATUS\G
Slave_IO_Running:Yes
Slave_SQL_Running:No
What are two reasons that you may stop the SQL thread on the slave while keeping the I/O thread running?
#在保持I/O线程运行的同时，可以停止从机上的SQL线程的两个原因是什么？
A、to allow the remaining events to be processed on the slave while not receiving new events from the master;
#允许在从机上处理剩余的事件，而不从主机接收新事件；
B、to allow a backup to be created under reduced load;
#允许在减少负载的情况下创建备份；
C、to allow for point-in-time recovery on the slave;
#允许从机上的时间点恢复；
D、to prevent schema changes from propagating to the slave before they are validated;
#防止模式更改在验证之前传播到从属服务器；
E、to prevent any transaction experiencing a deadlock;
#防止任何事务出现死锁；
Answer：BC；
A关闭 Slave_SQL_Running,slave 依旧要接收信息的,所以错
stopping only the SQL thread can be useful if you want to perform a backup or other task.
B.不进行 sql 应用， 降低负载
C.没有 sql 应用,所以能取到当时时间点的数据
D.防止用户没有经过验证的改变,应该是指的延迟复制， CHANGE MASTER TO MASTER_DELAY =N；
E.防止事务死锁， 没这效果
Stopping the I/O thread but permitting
the SQL thread to run helps ensure that there is not a massive backlog of events to be executed when replication is started again.
