烧脑
create table `t_bitfly` (
`id` bigint(20) not null default '0',
`value` varchar(32) default null,
primary key (`id`)
);
| Session A | Session B |
|---|---|
| start transaction; | start transaction; |
| select * from t_bitfly; empty set |
|
| insert into t_bitfly values (1, ‘a’); | |
| select * from t_bitfly; empty set |
|
| commit; | |
| select * from t_bitfly; empty set |
|
| insert into t_bitfly values (1, ‘a’); | |
| error 1062 (23000): duplicate entry ‘1’ for key 1 |
以为表里没有数据，其实数据已经存在了，傻乎乎的提交后，才发现数据冲突了
| Session A | Session B |
|---|---|
| start transaction; | start transaction; |
| select * from t_bitfly; 1 a |
|
| insert into t_bitfly values (2, ‘b’); | |
| select * from t_bitfly; 1 a |
|
| commit; | |
| select * from t_bitfly; 1 a |
|
| update t_bitfly set value=‘z’; | |
| Rows matched: 2 Changed: 2 Warnings: 0 (怎么多出来一行) |
第一次读取出一行，做了一次更新后，另一个事务里提交的数据就出现了。也可以看做是一种幻读?