Question

我有一个代码，无法计算如何计算值的出现次数，例如＆＃34; c＆＃34;的总和。 db中的数字是齿数，x表示缺牙，c表示龋齿，w表示填充。

 SELECT SUM(18='w'+17='w'+16='w'+15='w'+14='w'+13='w'+12='w'+11='w'+21='w'+22='w'+23='w'+24='w'+25='w'+26='w'+27='w'+28='w'+48='w'+47='w'+46='w'+45='w'+44='w'+44='w'+43='w'+42='w'+41='w'+31='w'+32='w'+33='w'+34='w'+35='w'+36='w'+37='w'+38='w') AS liczbaw FROM badania

表格如下：

Answer 1

首先要注意的是，您可能希望避免将列名称作为数字...根据＆＃34; Can a number be used to name a MySQL table column?＆＃34;，我必须引用后退（后退）引号）。

我实际上不确定您是要在多行上执行此操作，而是要聚合多行 - 您可以按以下方式执行操作

SELECT SUM(CASE WHEN `18` = 'c' THEN 1 ELSE 0 END) AS cnt_18_c FROM badania

所以，我在我的sql中使用CASE语句 - 您可以在＆＃34; Case statement in MySQL＆＃34;上找到更多信息。您也可以使用SUM(CASE...END) is synonymous to a SUM(IF(...))语句进行不同的操作。

如果您想要多个列和行，那么您只需添加您感兴趣的各个总和，如下所示：

SELECT
  SUM(CASE WHEN `18` = 'c' THEN 1 ELSE 0 END)
  + SUM(CASE WHEN `17` = 'c' THEN 1 ELSE 0 END) 
  AS cnt_18_17_c FROM badania

可以使用GROUP BY定义不同的分组（除了所有分组）。如果它是逐行的 - 那么甚至不需要SUM。

SELECT
 CASE WHEN `18` = 'c' THEN 1 ELSE 0 END
 + CASE WHEN `17` = 'c' THEN 1 ELSE 0 END
 AS cnt_18_17_c FROM badania

在后一种情况下，您还可以使用更智能的技术。您可以concatenate将所有牙齿作为字符串，并计算字符串中的出现次数，假设使用mysql的标准API集为您提供了这样的字符数。 - 或者您可以从编程环境（PHP）中完成计数。您还可以使用其他smart way to do those character counts。

所以我举了几个例子 - 希望我的MySQL语法正确。没有引用你确切的问题 - 我怀疑我可能已经覆盖了它。

Answer 2

该查询假设您想要查看特定患者，并且正在猜测如何完成此操作 - 相应地进行调整。如果要聚合所有患者，请删除where子句。

select tooth_code, count(*)
  from ( select 18 as tooth_code from badania where idb=2 and pacjent=25 union all
         select 17 from badania union where idb=2 and pacjent=25 all
         select 16 from badania union where idb=2 and pacjent=25 all
         select 15 from badania union where idb=2 and pacjent=25 all
         select 14 from badania union where idb=2 and pacjent=25 all
         select 13 from badania union where idb=2 and pacjent=25 all
         select 12 from badania union where idb=2 and pacjent=25 all
         select 11 from badania union where idb=2 and pacjent=25 all
         select 21 from badania union where idb=2 and pacjent=25 all
         select 22 from badania union where idb=2 and pacjent=25 all
         select 23 from badania union where idb=2 and pacjent=25 all
         select 24 from badania union where idb=2 and pacjent=25 all
         select 25 from badania union where idb=2 and pacjent=25 all
         select 26 from badania union where idb=2 and pacjent=25 all
         select 27 from badania union where idb=2 and pacjent=25 all
         select 28 from badania union where idb=2 and pacjent=25 all
         select 47 from badania union where idb=2 and pacjent=25 all
         select 46 from badania union where idb=2 and pacjent=25 all
         select 45 from badania union where idb=2 and pacjent=25 all
         select 44 from badania union where idb=2 and pacjent=25 all
         select 43 from badania union where idb=2 and pacjent=25 all
         select 42 from badania union where idb=2 and pacjent=25 all
         select 41 from badania union where idb=2 and pacjent=25 all
         select 31 from badania union where idb=2 and pacjent=25 all
         select 32 from badania union where idb=2 and pacjent=25 all
         select 33 from badania union where idb=2 and pacjent=25 all
         select 34 from badania where idb=2 and pacjent=25 union all
         select 35 from badania where idb=2 and pacjent=25 union all
         select 36 from badania where idb=2 and pacjent=25 union all
         select 37 from badania where idb=2 and pacjent=25 union all
         select 38 from badania where idb=2 and pacjent=25 
       ) 
   group by tooth_code

如何计算mysql行中某些值的出现次数？

2 个答案: