批量插入数据：
insert into actor(actor_id,first_name,last_name,last_update) values(1,‘PENELOPE‘,‘GUINESS‘,‘2006-02-15 12:34:33‘), (2,‘NICK‘,‘WAHLBERG‘,‘2006-02-15 12:34:33‘);
删除emp_no重复的记录，只保留最小的id对应的记录。
CREATE TABLE IF NOT EXISTS titles_test (
id int(11) not null primary key,
emp_no int(11) NOT NULL,
title varchar(50) NOT NULL,
from_date date NOT NULL,
to_date date DEFAULT NULL);
delete
from titles_test
where id not in (
select min(id) from titles_test
group by emp_no
)
sql 更新操作
update titles_test set from_date = ‘2001-01-01‘,to_date = NULL where to_date = ‘9999-01-01‘
原文：https://www.cnblogs.com/lijins/p/10349893.html