表 a ------ 表b ----- 表c
SELECT COUNT(*) FROM (SELECT a.字段,b.字段,c.字段 FROMa LEFT JOIN b ON a.id = b.id LEFT JOIN c ON a.id = b.id GROUP BY a.字段,b.字段) Z
表 a ------ 表b ----- 表c
SELECT COUNT(*) FROM (SELECT a.字段,b.字段,c.字段 FROMa LEFT JOIN b ON a.id = b.id LEFT JOIN c ON a.id = b.id GROUP BY a.字段,b.字段) Z