如果值为空，则包括计数0

Question

以下查询给出了结果，但我需要的是：

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

但是查询给出了结果：

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

查询：

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

我可以使用哪个函数来包含mysql的null值。我希望此查询与我的其他查询结果匹配，以便在将其转储到CSV文件

时不会发生冲突

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;