mysql join on 可以带and，例如：
SELECT pa.name as name, pa.sn as sn, re.created, sl.sn, re.phase, rd.times, ABS(sl.quantity) as quantity, dr.name as dname, dr.specifications as specifications
FROM rr AS re JOIN red AS rd ON re.id = rd.rid JOIN drug AS dr ON dr.id = rd.did JOIN {{bbbb}} AS sl ON re.id = sl.r_id AND sl.d_id = rd.d_id JOIN pp AS pa ON pa.id = re.p_id
WHERE $where AND sl.receive_id >0
用于将被join表没有对应数据的时候也可以将主join表的数据显示出来