mysql - 如何计算 mysql 中计数列中值的总和？

Question

我有一个非常复杂的数据库，我正在尝试执行一个查询，该查询返回结果计数列的所有值的总和。我可以成功确定计数值，但如何确定总和？

我的代码是:

SELECT COUNT(cause) as num_of_deaths
FROM deaths
WHERE rlist IN ('09A', '09B', '09N', '09C') 
AND ryear IN (SELECT DISTINCT ryear FROM deaths)
AND cause IN (SELECT cause FROM icd9 WHERE description LIKE '%MN OF%')
GROUP BY cause;

每次我尝试将我的计数包含在 SUM 中时，我都会收到一条错误消息，提示“组函数的使用无效”。我该如何解决这个问题？

我的结果集如下所示:resultant set

Answer 1

你试过吗:

SELECT SUM(num_of_deaths) FROM (
SELECT COUNT(cause) as num_of_deaths
FROM deaths
WHERE rlist IN ('09A', '09B', '09N', '09C') 
AND ryear IN (SELECT DISTINCT ryear FROM deaths)
AND cause IN (SELECT cause FROM icd9 WHERE description LIKE '%MN OF%')
GROUP BY cause) as nums_of_deaths;