Question

我有一个按日期差异排序的查询。我的排序目前正在工作，但我想使用案例如

如果priority<=10 THEN 10将添加当前优先级

我的查询当前返回修改优先级值的默认异常值

我的查询是

SELECT videoid,priority, 
      CASE WHEN priority<=10 THEN (priority+10)
           WHEN priority>10 and priority<=20 THEN (priority+9)
           WHEN priority<=30 THEN (priority+8) 
      END AS 'modified_priority', 
      DATEDIFF(CURDATE(),
      DATE(from_unixtime(submittime))) AS d 
FROM 
  `datatable` 
ORDER BY d

Answer 1

你的最后一个案例与所有人相匹配试试这个

SELECT videoid,priority, 
      CASE WHEN priority <=10 THEN (priority+10)
           WHEN priority>10 and priority <=20 THEN (priority+9)
           WHEN priority>20 AND priority <=30 THEN (priority+8) 
      END AS `modified_priority`, 
      DATEDIFF(CURDATE(),
      DATE(from_unixtime(submittime))) AS d 
FROM 
  `datatable` 
ORDER BY d

Answer 2

按顺序处理Case语句，返回第一个匹配条件。您可以使用此优势并将语句简化为：

SELECT videoid, priority, 
       (CASE WHEN priority <= 10 THEN (priority+10)
             WHEN priority <= 20 THEN (priority+9)
             WHEN priority <= 30 THEN (priority+8) 
        END) AS modified_priority, 
       DATEDIFF(CURDATE(), DATE(from_unixtime(submittime))) AS d 
FROM `datatable` 
ORDER BY d;

如果您不希望返回NULL的优先级值大于30，那么您需要一个ELSE子句。也许：

SELECT videoid, priority, 
       (CASE WHEN priority <= 10 THEN (priority+10)
             WHEN priority <= 20 THEN (priority+9)
             WHEN priority <= 30 THEN (priority+8) 
             ELSE priority
        END) AS modified_priority, 
       DATEDIFF(CURDATE(), DATE(from_unixtime(submittime))) AS d 
FROM `datatable` 
ORDER BY d;

另外，我从modified_priority左右删除了单引号。您应该只对字符串和日期常量使用单引号。

带有case语句的mysql查询

2 个答案: