前面介绍了使用insert实现新增和修改记录的使用姿势,接下来我们看一下另外一个简单的使用方式,如何删除数据

1. delete 语句

delete的官方语法如下

DELETE FROM <measurement_name> WHERE [<tag_key>='<tag_value>'] | [<time interval>]

delete语句和我们常见sql语法有点像,但是注意一下上面的where中的条件,只允许根据tag和时间来进行删除操作

下面给出几个简单的例子

case1 根据时间删除

> select * from add_test
name: add_test
time                age boy  email            name  phone user_id
----                --- ---  -----            ----  ----- -------
1564149327925320596 19  true bangzewu@126.com YiHui 110   0
1564149920283253824 18  true bangzewu@126.com YiHui 110   21
1564150279123000000 18  true bangzewu@126.com YiHui 110   22
> delete from add_test where time>=1564150279123000000
> select * from add_test
name: add_test
time                age boy  email            name  phone user_id
----                --- ---  -----            ----  ----- -------
1564149327925320596 19  true bangzewu@126.com YiHui 110   0
1564149920283253824 18  true bangzewu@126.com YiHui 110   21

case2 根据tag删除

注意name为保留名,因此需要用双引号括起来

> show tag keys from add_test
name: add_test
tagKey
------
name
phone
> delete from add_test where "name"='YiHui'
> select * from add_test
>

2. 不同保存策略的数据删除

从前面的语法定义中,没有看到指定保留策略的情况,那么如果需要删除某个保存策略的数据,应该怎样?

> insert add_test,name=YiHui,phone=110 boy=true,age=19i,user_id=2
> insert into "1D" add_test,name=YiHui,phone=110 boy=true,age=19i,user_id=1
> select * from add_test
name: add_test
time                age boy  name  phone user_id
----                --- ---  ----  ----- -------
1564483471390538399 19  true YiHui 110   2
> select * from "1D".add_test
name: add_test
time                age boy  name  phone user_id
----                --- ---  ----  ----- -------
1564483483748916258 19  true YiHui 110   1

> delete from add_test where "name"='YiHui'
> select * from add_test
> select * from "1D".add_test
>

执行上面的case之后,发现根据tag进行删除时,默认策略,和"1D"保存策略中的数据都被删除掉了

下面是另外一个验证

> select * from add_test;
name: add_test
time                age boy  name  phone user_id
----                --- ---  ----  ----- -------
1564483778197609864 19  true YiHui 110   1
> insert into "2_h"  add_test,name=YiHui,phone=110 boy=true,age=19i,user_id=1
> select * from "2_h".add_test;
name: add_test
time                age boy  name  phone user_id
----                --- ---  ----  ----- -------
1564483793280811751 19  true YiHui 110   1
> delete from add_test where time=1564483793280811751
> select * from "2_h".add_test;
> select * from add_test;
name: add_test
time                age boy  name  phone user_id
----                --- ---  ----  ----- -------
1564483778197609864 19  true YiHui 110   1

我们在"2_h"这个策略中新增了一条数据,直接根据时间进行删除,当前的策略下的数据没有影响,"2_h"策略中刚添加的数据被删除掉了