你知道为什么这个查询对mariadb不起作用吗？它似乎遵循mariadb文档站点上的模式

SELECT ...
(INTERSECT | EXCEPT | UNION [ALL | DISTINCT]) SELECT ...

( SELECT t1.visitid, t1. patientid, t1.visitdate
FROM db.medi_officevisit t1
WHERE t1.visitdate = (SELECT t2.visitdate
                 FROM db.medi_officevisit t2
                 WHERE t2.PatientID = t1.PatientID and VISITdate >= '2018-01-01'
                 ORDER BY t2.visitID DESC
                 LIMIT 1) )
EXCEPT
( SELECT t1.visitid, t1. patientid, t1.visitdate
FROM db.medi_officevisit t1
WHERE t1.visitdate = (SELECT t2.visitdate
                 FROM db.medi_officevisit t2
                 WHERE t2.PatientID = t1.PatientID and VISITdate >= '2017-01-01' and VISITDATE <= '2018-01-01'  
                 ORDER BY t2.visitID DESC
                 LIMIT 1) );

错误代码：1064。sql语法有错误；检查与您的mariadb服务器版本相对应的手册，以了解使用“except（select t1.visitid，t1）”附近的正确语法。patientid，t1.8号线医务室探视日期