为什么函数SUM不会工作SQL

Question

我的SUM（）在按帐户ID ID分组时，不会添加女性学生人数

这里是查询

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结果如下 Result of the Query

Answer 1

您正在按错误的列进行分组。如果您希望注册不同课程的学生人数，则必须按course分组，而不是temporary_answers

Answer 2

查询中几乎没有问题，无需将sex = "Female"写为条件有tbl_temporary.sex = "Female"的地方。你需要为此if else写sum(if (course = "BSCS", 1, 0))。所以改变查询和检查。并在if if列名称中更改 1

SELECT 
   firstname,
   middlename,
   lastname,
   SUM(if (course = "BSCS", 1, 0)) as BSCS,
   SUM(if (course = "BSIT", 1, 0)) as BSIT,
   SUM(if (course = "BSIS", 1, 0)) as BSIS,
   sex,
   course from tbl_temporary 
WHERE tbl_temporary.sex = "Female" GROUP BY temporary_answer