SQL语句 年月日中获取月份和日期

表 ：ST_RSVRFSR_B

表：ST_RSVR_R

问题：通过关联stcd关联两个表，查找出RZ大于FSLTDZ的字段，切tm字段与BGMD和EDMD的日期对应上。

tm是DATETIME类型，BGMD和EDMD是char类型

---

SQL语句

SELECT  rsvr.TM,rsvr.STCD,rsvr.RZ,rsversr.FSLTDZ,rsversr.BGMD,rsversr.EDMD
FROM    ST_RSVR_R rsvr inner join ST_RSVRFSR_B rsversr
ON rsvr.STCD=rsversr.STCD 
where rsvr.RZ>rsversr.FSLTDZ AND (CASE LEN(MONTH(TM))
              WHEN 1 THEN '0' + CONVERT(VARCHAR, MONTH(TM))
              ELSE CONVERT(VARCHAR, MONTH(TM))
            END+CASE LEN(DAY(TM))
              WHEN 1 THEN '0' + CONVERT(VARCHAR, DAY(TM))
              ELSE CONVERT(VARCHAR, DAY(TM))
            END)>rsversr.BGMD AND (CASE LEN(MONTH(TM))
              WHEN 1 THEN '0' + CONVERT(VARCHAR, MONTH(TM))
              ELSE CONVERT(VARCHAR, MONTH(TM))
            END+CASE LEN(DAY(TM))
              WHEN 1 THEN '0' + CONVERT(VARCHAR, DAY(TM))
              ELSE CONVERT(VARCHAR, DAY(TM))
            END)