$selectedmonth = '09';
$selectedyear = '2019';
$selecteduser = '1';
假设我有上述变量,我的mysql查询就是这样
SELECT `USERID`, `CHECKTIME` FROM `checkinout` WHERE USERID='$selecteduser' AND YEAR(CHECKTIME)= '$selectedyear' AND MONTH(CHECKTIME)='$selectedmonth'
我如何修改mysql查询以搜索选定月份和选定月份的下个月第一天的记录?