MYSQL 怎么 LEFT JOIN 多表联查

三表联查：

SELECT ,,DATE_FORMAT(FROM_UNIXTIME(),'%Y-%m-%d %H:%i:%s') as time,
from  a LEFT JOIN b ON  =  
LEFT JOIN c ON  = 
WHERE  BETWEEN 1542902400 AND 1542988799 AND  = 624  

二表联查：

SELECT ,,DATE_FORMAT(FROM_UNIXTIME(),'%Y-%m-%d %H:%i:%s') as time
from  a LEFT JOIN b ON  =  
WHERE  BETWEEN 1542902400 AND 1542988799 AND  = 624  

其他查询，大致相似，自己可以借鉴研究一下