语句分析：如果不存在某时段的数据，会显示为null，如何将不存在的时段自动补齐呢？

select a.lockdate,ifnull(b.count,0) as count
from (SELECT 0  as lockdateunion allSELECT 1 as lockdateunion allSELECT 2 as lockdateunion allSELECT 3 as lockdateunion allSELECT 4 as lockdateunion allSELECT 5 as lockdateunion allSELECT 6 as lockdateunion allSELECT 7 as lockdateunion allSELECT 8 as lockdateunion allSELECT 9 as lockdateunion allSELECT 10 as lockdateunion allSELECT 11 as lockdateunion allSELECT 12 as lockdateunion allSELECT 13 as lockdateunion allSELECT 14 as lockdateunion allSELECT 15 as lockdateunion allSELECT 16 as lockdateunion allSELECT 17 as lockdateunion allSELECT 18 as lockdateunion allSELECT 19 as lockdateunion allSELECT 20 as lockdateunion allSELECT 21 as lockdateunion allSELECT 22 as lockdateunion allSELECT 23 as lockdate
) a left join (SELECTHOUR (login_time) AS hoursFROMtb_log_loginWHEREDATE_FORMAT(login_time, '%Y-%m-%d') = DATE_FORMAT('2020-07-31', '%Y-%m-%d')GROUP BYhours
) b on a.lockdate = b.hours;

Done！