MySQL的情况下，地方“只适用于一定的价值

Question

我下面的表格有：

id | date_inserted | type  | route_id | route_type | km 
1 2016-01-05  Transport null  Normal  null 
2 2016-01-06  Transport null  Normal  50 
3 2016-01-07  Transport 1   Normal  null 
4 2016-04-02  Transport 2   Normal  null 
5 2016-05-03  Services  null  Normal  20 
6 2016-06-21  Transport null  Exceptional 35 

，我需要通过几个月来检索总的路线。这是通过执行实现：

SELECT type, COUNT(id) AS `total`, MONTH(date_inserted) AS `month` 
FROM routes 
WHERE YEAR(date_inserted) = '2016' AND 
     type IN ('Transport', 'Services') 
GROUP BY type, `month` 
ORDER BY date_inserted ASC, `total` DESC 

的输出是一样的东西：

type  | total | month 
Transport 3  1 
Transport 1  2 
Services  1  5 
Transport 1  6 

，它工作正常。不过，现在有人问我申请了一些条件，只有当类型是Transport，条件如下：

1. 的route_id不能为null或
2. 的route_type必须Exceptional或
3. 的route_type是Normal和km不等于零

所以，根据这个条件，这是我已经试过：

SELECT type, COUNT(id) AS `total`, MONTH(date_inserted) AS `month` 
FROM routes 
WHERE YEAR(date_inserted) = '2016' AND 
     type IN ('Transport', 'Services') AND 
     (CASE WHEN type = 'Transport' THEN 
      route_id IS NOT NULL OR 
      route_type = 'Exceptional' OR 
      (route_type = 'Normal' AND km != 0) 
     END) 
GROUP BY type, `month` 
ORDER BY date_inserted ASC, `total` DESC 

但我的输出是：

type  | total | month 
Transport 2  1 
Transport 1  2 
Transport 1  6 

的Services行缺少。

Answer 1

您需要添加一个else段来处理服务。如果你想的情况下是允许正常处理使用1 = 1

SELECT type, COUNT(id) AS `total`, MONTH(date_inserted) AS `month` 
FROM routes 
WHERE YEAR(date_inserted) = '2016' AND 
    type IN ('Transport', 'Services') AND 
    (CASE WHEN type = 'Transport' THEN 
     route_id IS NOT NULL OR 
     route_type = 'Exceptional' OR 
     (route_type = 'Normal' AND km != 0) 
    ELSE 
    1 = 1 
    END) 
GROUP BY type, `month` 
ORDER BY date_inserted ASC, `total` DESC 

Answer 2

正如其他人说，你需要一个ELSE添加到您的情况下，否则当行是“服务”，它会返回null，不显示记录。

SELECT type, COUNT(id) AS `total`, MONTH(date_inserted) AS `month` 
FROM routes 
WHERE YEAR(date_inserted) = '2016' AND 
     type IN ('Transport', 'Services') AND 
     (CASE WHEN type = 'Transport' THEN 
      route_id IS NOT NULL OR 
      route_type = 'Exceptional' OR 
      (route_type = 'Normal' AND km != 0) 
      ELSE 1 = 1 
     END) 
GROUP BY type, `month` 
ORDER BY date_inserted ASC, `total` DESC; 

另一个版本，你可以使用（我喜欢）是：

SELECT type, COUNT(id) AS `total`, MONTH(date_inserted) AS `month` 
FROM routes 
WHERE YEAR(date_inserted) = '2016' AND 
     (type = 'Services' OR 
      (type = 'Transport' and 
        (route_id IS NOT NULL OR 
         route_type = 'Exceptional' OR 
         (route_type = 'Normal' AND km != 0) 
        ) 
     ) 
    ) 
GROUP BY type, `month` 
ORDER BY date_inserted ASC, `total` DESC; 

如果route_type只能是Normal和Exceptional您可以更改条件：

SELECT type, COUNT(id) AS `total`, MONTH(date_inserted) AS `month` 
FROM routes 
WHERE YEAR(date_inserted) = '2016' AND 
     (type = 'Services' OR 
      (type = 'Transport' and 
        (route_id IS NOT NULL OR 
        route_type = 'Exceptional' OR 
        km != 0 
        ) 
     ) 
    ) 
GROUP BY type, `month` 
ORDER BY date_inserted ASC, `total` DESC;