### API
https://docs.influxdata.com/influxdb/v0.13/concepts/api/
## write 
curl -i -XPOST 'http://192.168.1.12:8086/write?db=test_dba' --data-binary 'cpu_load_short,host=server01,region=us-west value=0.64 1434055562000000000'

## query
# pretty=true， 以json格式输出
curl -GET 'http://192.168.1.12:8086/query?pretty=true' --data-urlencode "db=test_dba" --data-urlencode "q=SELECT host,value FROM cpu_load_short WHERE region='us-west'"

# epoch=s， 将time列以s的格式输出
curl -GET 'http://192.168.1.12:8086/query?pretty=true' --data-urlencode "db=test_dba" --data-urlencode "epoch=s"  --data-urlencode "q=SELECT last(value) FROM test_msmts4"

### sql
# u microseconds, s seconds, m minutes, h hours, d days, w weeks
SELECT * FROM foodships WHERE time > '2015-04-16 12:00:01'
SELECT * FROM foodships WHERE time > now() - 1h

# 将时间按每30分钟一个组
group by time(30m)

## 支持的函数
https://docs.influxdata.com/influxdb/v0.13/query_language/functions/
# count(field) ，不支持count(*)
按 time值做 Aggregation 

# MEAN(field), field必须是数值类型
求field 平均值

# BOTTOM(<field_key>[,<tag_keys>],<N>)[,<tag_keys>]
# TOP(<field_key>[,<tag_keys>],<N>)[,<tag_keys>]
取最小/大的前几个值，也可以在指定tag

# FIRST(<field_key>)[,<tag_key(s)>]
# LAST(<field_key>)[,<tag_key(s)>] 
取最老/新的值

# PERCENTILE(<field_key>, <N>)[,<tag_key(s)>]
取 field中大于N%的值

# STDDEV(<field_key>) 

# DIFFERENCE(<field_key>)