怎么查出连续上班的的天数
表tb_chuqin中有
empno        workdt           worktime      overtime
2130101      20130112           0               0
2130101      20130111           480             0
2130101      20130110           480             60
2130101      20130109           480             0
2130101      20130108           480             60
2130101      20130107           480             60
2130101      20130106           480             60
2130101      20130105           480             60
2130101      20130104           480             60
2130101      20130103           480             60
2130101      20130102           480             60
2130101      20130101           480             30
2130101      20121228           480             0
2130101      20121229           480             60
2130101      20121230           480             0
2130101      20121231           480             120
2130801      20121230           480             0



表tb_kaoqin中有

empno            workdt              timecd   
2130101&nbs