1.以默认方式启动事务1，修改事务隔离级别，查看 transaction_isolation
begin;
show transaction_isolation;
end;
START TRANSACTION;
show transaction_isolation;
END;
2.以读写方式启动事务2，创建新表，修改事务为只读事务，查看 transaction_read_only，并向表中插入记录
BEGIN;
SET LOCAL TRANSACTION ISOLATION LEVEL READ COMMITTED READ WRITE;
show transaction_isolation;
create table test1(a int,b varchar(10));
SET LOCAL TRANSACTION ISOLATION LEVEL READ COMMITTED READ ONLY;
show transaction_read_only;
insert into test1 values(1,'zhangsan');
select * from test1;
commit;
3.启动事务3，对表进行增删改查，并用到创建savepoint，回滚savepoint和删除savepoint
create table test(a int,b varchar(10));
START TRANSACTION;
insert into test values(1,'zhangsan');
–建立保存点
SAVEPOINT test_savepoint;
insert into test values(2,'zhangsan');
–回滚保存点
ROLLBACK TO SAVEPOINT test_savepoint;
–删除保存点
RELEASE SAVEPOINT test_savepoint;
insert into test values(3,'zhangsan');
COMMIT;
–查询表的内容
SELECT * FROM test;
4.清理数据
drop table test;
