mysql日期格式化

1 select DATE_FORMAT(dtl.transdate,'%Y-%m-%d') as transdate,
2         right(DATE_FORMAT(concat(transdate,transtime),'%Y-%m-%d %H:%i:%s'),8) as
3         transtime,dtl.custname,dtl.stuempno,dtl.deviceid,dtl.devtype,dev.devicename,a.names as areaname
4         from t_devicedtl dtl
5         left join t_device dev on dev.deviceid=dtl.deviceid
6         left join t_area a on a.id=dev.areaid

DATE_FORMAT(dtl.transdate,'%Y-%m-%d') ：例如将数据库中的transdate字段20200123进行格式化，结果为：2020-01-23
DATE_FORMAT(concat(transdate,transtime),'%Y-%m-%d %H:%i:%s')：例如字段transdate:20200123,字段transtime:122359,结果为：2020-01-23 12:23:59
right(DATE_FORMAT(concat(transdate,transtime),'%Y-%m-%d %H:%i:%s'),8) :取格式化后取后8位，结果为：12:23:59