sql 语句

分组,个数

select frameIDName,count(*) from tb_chargeparsing GROUP BY frameIDName

 

时间格式转化

sqlserver

string 转 datetime

SELECT convert(datetime, '2016-10-23 20:44:11',      120) -- yyyy-mm-dd hh:mm:ss(24h)

-- 2016-10-23 20:44:11.000

SELECT convert(datetime, '2016-10-23 20:44:11.500',  121) -- yyyy-mm-dd hh:mm:ss.mmm

mysql
 --string 转 datetime
STR_TO_DATE('2021-10-22 18:56:44','%Y-%m-%d %H:%i:%s')

-- datetime 转 string
date_format(a.time,'%H:%i:%s')

 

获取插入自增ID(按连接Connection分离)

SELECT LAST_INSERT_ID();

 

 

联合查询

select *,d.accuracyLevel as d_accuracyLevel,p.accuracyLevel as p_accuracyLevel from tb_deviceinfo as d left join tb_pileinfo as p on d.pID=p.ID where deviceID='{json.deviceID}'

 

分组查询

select p.*,d.ID as dID,group_concat(d.ID) as count from tb_pileinfo as p left join tb_deviceinfo as d on p.ID=d.pID where p.userID=1  GROUP BY p.ID

group_concat(d.ID)  所有项列举 
count(*) 分组各组数量