包括以下查詢給出結果，但我需要的是數0，如果值是空

Question

的：

city_name | total | 
+-----------+-------+ 
| Bangalore | 13 | 
| Mumbai | 21 | 
| Coimbatore|  0 | 
| Madurai |  0 | 
| salem  |  0 | 
| Chennai |  4 | 
| Pune  | 30 | 
| Ghaziabad |  1 | 
| Gurgaon |  2 | 

但查詢給出結果：

+-----------+-------+ 
| city_name | total | 
+-----------+-------+ 
| Bangalore | 13 | 
| Mumbai | 21 | 
| Chennai |  4 | 
| Pune  | 30 | 
| Ghaziabad |  1 | 
| Gurgaon |  2 | 
+-----------+-------+ 

查詢：

select c.city_name,count(distinct r.restaurant_id) as total from restaurants r 
            left join je_restaurant_status jrs on r.restaurant_id = jrs.restaurant_id 
            left join locations l on l.location_id = r.location_id 
            left outer join cities c on c.city_id = l.city_id                        where jrs.update_date < '2014-10-01 00:00:00'       
            and jrs.registered=1 and jrs.operations_closed = 0 and jrs.temporary_disabled=1                group by c.city_id 

我可以使用哪個函數來包含來自mysql的空值。我希望此查詢與我的其他查詢結果相匹配，以便在將其轉儲到CSV文件時不會發生衝突

Answer 1

select c.city_name,count(distinct r.restaurant_id) as total from restaurants r         
inner join status jrs on r.restaurant_id = jrs.restaurant_id           
inner join locations l on l.location_id = r.location_id           
right join cities c on c.city_id = l.city_id                    
where jrs.update_date < '2014-10-01 00:00:00'and 
jrs.registered=1 and jrs.operations_closed = 0           
group by c.city_id;