openGauss每日一练第 16天|事务控制

学习openGauss事务控制

事务是用户定义的一个数据库操作序列，这些操作要么全做要么全不做，是一个不可分割的工作单位

1.以默认方式启动事务1，修改事务隔离级别，查看transaction_isolation

– 默认方式启动事务

start transaction; 
select relname from pg_class limit 5;
end;

– 修改事务隔离级别

begin;
show transaction_isolation;
SET LOCAL TRANSACTION ISOLATION LEVEL REPEATABLE READ;
show transaction_isolation;
end;

– 查看事务隔离级别

show transaction_isolation;

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

–以隔离级别为repeatable read，读/写方式启动事务

show transaction_isolation;
START TRANSACTION ISOLATION LEVEL repeatable read READ WRITE;
show transaction_isolation;
show transaction_read_only;

create table demo_t1(id int);
insert into demo_t1 values (1),(2),(3),(4),(5);
select * from demo_t1;

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

start transaction;
insert into demo_t1 values (11);
select * from demo_t1;

–建立保存点

savepoint save_t1;
insert into demo_t1 values (22);
select * from demo_t1;

–回滚保存点

rollback to savepoint save_t1;
select * from demo_t1;

–删除保存点

release savepoint save_t1;
select * from demo_t1;

4.清理数据

drop table demo_t1;