1 #----综合使用
 2 书写顺序
 3 select distinct * from '表名' where '限制条件'  group by '分组依据' having '过滤条件' order by  limit '展示条数'
 4 执行顺序
 5 from       -- 查询
 6 where      -- 限制条件
 7 group by   -- 分组
 8 having     -- 过滤条件
 9 order by   -- 排序
10 limit      -- 展示条数
11 distinct   -- 去重
12 select     -- 查询的结果

1.查询数据表weather 的所有记录:

> select * from weather
name: weather
time altitude area humidity temperature
---- -------- ---- -------- -----------
1607604432455278300 1001 南 -5 10
1607656595672442800 1000 东 -4 9
1607656662027484500 1001 南 -5 11
1607656706278952000 999 南 -5 11
1607656751612223600 1002 西 -2 11
1607656799728402900 1003 东 -2 11

2.按条件查询

#查询temperature=11的数据
> select * from weather where temperature=11
name: weather
time                altitude area humidity temperature
----                -------- ---- -------- -----------
1607656662027484500 1001     南    -5       11
1607656706278952000 999      南    -5       11
1607656751612223600 1002     西    -2       11
1607656799728402900 1003     东    -2       11
> select altitude,temperature from weather
name: weather
time                altitude temperature
----                -------- -----------
1607604432455278300 1001     10
1607656595672442800 1000     9
1607656662027484500 1001     11
1607656706278952000 999      11
1607656751612223600 1002     11
1607656799728402900 1003     11

#按最新时间排序
> select * from weather order by time desc
name: weather
time                altitude area humidity temperature
----                -------- ---- -------- -----------
1607656799728402900 1003     东    -2       11
1607656751612223600 1002     西    -2       11
1607656706278952000 999      南    -5       11
1607656662027484500 1001     南    -5       11
1607656595672442800 1000     东    -4       9
1607604432455278300 1001     南    -5       10
#按最早时间排序
> select * from weather order by time asc
name: weather
time                altitude area humidity temperature
----                -------- ---- -------- -----------
1607604432455278300 1001     南    -5       10
1607656595672442800 1000     东    -4       9
1607656662027484500 1001     南    -5       11
1607656706278952000 999      南    -5       11
1607656751612223600 1002     西    -2       11
1607656799728402900 1003     东    -2       11
4.去重 (distinct)
> select distinct humidity from weather
name: weather
time distinct
---- --------
0    -5
0    -4
0    -2
5.group by
select 查询字段1,查询字段2,... from 表名
      where 过滤条件
      group by分组依据  # 分组后取出的是每个组的第一条数据
> select * from weather group by area
name: weather
tags: area=东
time                altitude humidity temperature
----                -------- -------- -----------
1607656595672442800 1000     -4       9
1607656799728402900 1003     -2       11
name: weather
tags: area=南
time                altitude humidity temperature
----                -------- -------- -----------
1607604432455278300 1001     -5       10
1607656662027484500 1001     -5       11
1607656706278952000 999      -5       11
name: weather
tags: area=西
time                altitude humidity temperature
----                -------- -------- -----------
1607656751612223600 1002     -2       11
 ①count()函数




    

返回一个（field）字段中的非空值的数量。
SELECT COUNT(<field_key>) FROM <measurement_name> [WHERE <stuff>] [GROUP BY <stuff>]
> select count(humidity) from weather
name: weather
time count
---- -----
②MEAN() 函数
返回一个字段（field）中的值的算术平均值（平均值）。字段类型必须是长整型或float64。
语法格式：SELECT MEAN(<field_key>) FROM <measurement_name> [WHERE <stuff>] [GROUP BY <stuff>]
> SELECT MEAN(humidity) from weather
name: weather
time mean
---- ----
0    -3.8333333333333335
③MEDIAN()函数
从单个字段（field）中的排序值返回中间值（中位数）。中值是在一组数值中居于中间的数值。字段值的类型必须是长整型或float64格式。
语法：SELECT MEDIAN(<field_key>) FROM <measurement_name> [WHERE <stuff>] [GROUP BY <stuff>]
> SELECT MEAN(humidity) from weather
name: weather
time mean
---- ----
0    -3.8333333333333335
④SPREAD()函数
返回字段的最小值和最大值之间的差值。数据的类型必须是长整型或float64。
语法：SELECT SPREAD(<field_key>) FROM <measurement_name> [WHERE <stuff>] [GROUP BY <stuff>]

> select spread(humidity) from weather
name: weather
time spread
---- ------
⑤SUM()函数
返回一个字段中的所有值的和。字段的类型必须是长整型或float64。
语法：SELECT SUM(<field_key>) FROM <measurement_name> [WHERE <stuff>] [GROUP BY <stuff>
> select sum(humidity) from weather
name: weather
time sum
---- ---
0    -23
⑥INTEGRAL()函数
语法：SELECT INTEGRAL( [ * | <field_key> | /<regular_expression>/ ] [ , <unit> ] ) [INTO_clause] FROM_clause [WHERE_clause] [GROUP_BY_clause] [ORDER_BY_clause] [LIMIT_clause] [OFFSET_clause] [SLIMIT_clause] [SOFFSET_clause] 
> select INTEGRAL(temperature) from weather
name: weather
time integral
---- --------
0    497728.82358215
⑦distinc()函数
> select distinct(temperature) from weather
name: weather
time distinct
---- --------
0    10
0    11
7.limit限制条数
#显示一条信息
> select * from weather limit 1
name: weather
time                altitude area humidity temperature
----                -------- ---- -------- -----------
1607604432455278300 1001     南    -5       10
#limit 10 offset 15，就是从第15行开始之后的10条数据
> select * from weather limit 2 offset 2
name: weather
time                altitude area humidity temperature
----                -------- ---- -------- -----------
1607656662027484500 1001     南    -5       11
1607656706278952000 999      南    -5       11
influxDB中没有in的操作，但是有or。对于习惯了mysql的in来说，用or就需要在代码中循环了。
> select * from weather where altitude=1001 or temperature=11
name: weather
time                altitude area humidity temperature
----                -------- ---- -------- -----------
1607656662027484500 1001     南    -5       11
1607656706278952000 999      南    -5       11
1607656751612223600 1002     西    -2       11
1607656799728402900 1003     东    -2       11
9.模糊查询
> select * from test
name: test
time                app count host      monitor_name num
----                --- ----- ----      ------------ ---
1585897703920290000     1     127.0.0.1 test         
1585897983909417000 ios 2     127.0.0.1 test1        3
1585898383503216000 ios 2     127.0.0.1 test1        3
1585901694441000000 ios 2     127.0.0.1 app1         3
1585901704179677000 ios 2     127.0.0.1 ios1         3
## =~/给定字段/ 包含指定字段的
> select * from test where monitor_name =~/app/
name: test
time                app count host      monitor_name num
----                --- ----- ----      ------------ ---
1585901694441000000 ios 2     127.0.0.1 app1         3
##=~/^给定字段/ 以指定字段开始的
> select * from test where monitor_name =~/^app/
name: test
time                app count host      monitor_name num
----                --- ----- ----      ------------ ---
1585901694441000000 ios 2     127.0.0.1 app1         3
##=~/给定字段$/ 以指定字段结尾的
> select * from test where monitor_name =~/p1$/
name: test
time                app count host      monitor_name num
----                --- ----- ----      ------------ ---
1585901694441000000 ios 2     127.0.0.1 app1         3
10.展示tag
> show tag keys from weather
name: weather
tagKey
------
altitude
#查询单个tag的value值
#查询所以tag为altitude的value的值
> show tag values from weather with key="altitude"
name: weather
key      value
---      -----
altitude 1000
altitude 1001
altitude 1002
altitude 1003
altitude 999