redis它只是做到了：
- 它认为的原子性。（单个命令原子，多条命令不一定原子）
- 隔离性。（单线程执行，各事务串行执行，天然满足隔离）
- AOF/RDB保证了部分的持久性。（持久化的时候可能存在数据丢失）
- 它不存在ACID中的C的概念，因为它没有约束。
1. 命令使用错误
这种错误redis在执行前就能检查出来，因此整个事务都不执行。
127.0.0.1:6379> get name
"xumeili"
127.0.0.1:6379> get age
"28"
127.0.0.1:6379> get sex
"female"
127.0.0.1:6379> multi
OK
127.0.0.1:6379> set name xuzhijun
QUEUED
127.0.0.1:6379> set age
(error) ERR wrong number of arguments for 'set' command
127.0.0.1:6379> set sex male
QUEUED
127.0.0.1:6379> exec
(error) EXECABORT Transaction discarded because of previous errors.
127.0.0.1:6379> get name
"xumeili"
127.0.0.1:6379> get age
"28"
127.0.0.1:6379> get sex
"female"
2. 命令执行错误
这种错误redis无法在执行前发现，因此不影响这种错误的前后命令被提交。
127.0.0.1:6379> get name
"xumeili"
127.0.0.1:6379> get age
"28"
127.0.0.1:6379> get sex
"female"
127.0.0.1:6379> multi
OK
127.0.0.1:6379> set name tony
QUEUED
127.0.0.1:6379> sadd age 100
QUEUED
127.0.0.1:6379> set sex male
QUEUED
127.0.0.1:6379> exec
1) OK
2) (error) WRONGTYPE Operation against a key holding the wrong kind of value
3) OK
127.0.0.1:6379> get name
"tony"
127.0.0.1:6379> get age
"28"
127.0.0.1:6379> get sex
"male"
3. 使用watch
事务内key值发生变化，整个事务不提交。
session1:
127.0.0.1:6379> get name
"xuzhijun"
127.0.0.1:6379> get age
"300"
127.0.0.1:6379> get sex
"female"
127.0.0.1:6379> watch age
OK
127.0.0.1:6379> multi
OK
127.0.0.1:6379> set name tony
QUEUED
127.0.0.1:6379> set age 100
QUEUED
127.0.0.1:6379> set sex male
QUEUED
127.0.0.1:6379> exec
(nil)
127.0.0.1:6379> get name
"xuzhijun"
127.0.0.1:6379> get age
"28"
127.0.0.1:6379> get sex
"female"
session2:
127.0.0.1:6379> set age 28
OK
127.0.0.1:6379> get age
"28"
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