1.需求:当前系统时间一个月前每天的预警台数
2.现在我写的SQL只会显示出有数据的日期的总条数,求大佬们加个条件
没有条数的日期也显示出来 条数显示为0
SELECT
aed_warn.lasttime,
count( aed_warn.id ) AS number
FROM
aed_warn
LEFT JOIN aed_device ON aed_warn.deviceid = aed_device.id
WHERE
aed_device.setupcity = "深圳市"
AND aed_warn.lasttime BETWEEN ( SELECT DATE_ADD( now( ), INTERVAL - 1 MONTH ) )
AND now( )
GROUP BY
lasttime;