Question

select student_id, class_id, section_id, exam_date, exam_id, 
       sum(number*(1-abs(sign(subject-1)))) as sub1, 
       sum(number*(1-abs(sign(subject-2)))) as sub2, 
       sum(number*(1-abs(sign(subject-3)))) as sub3, 
       sum(number*(1-abs(sign(subject-4)))) as sub4, 
       sum(number*(1-abs(sign(subject-5)))) as sub5, 
       sum(number*(1-abs(sign(subject-6)))) as sub6 
from result 
where class_id = '7' and section id = '3' and YEAR(exam_date) = '2012' and exam_id = '3'
GROUP BY student_id

我有一个问题，当我使用where子句过滤时，所有数值都为0，如果我在没有where子句的情况下运行查询，结果会很好但是来自所有数据库。如何使用where子句过滤查询？任何人都可以帮助我吗？

Answer 1

将查询包裹在where。

之前

SELECT * FROM (
select student_id, class_id, 
       sum(number*(1-abs(sign(subject-1)))) as sub1, 
       sum(number*(1-abs(sign(subject-2)))) as sub2, 
       sum(number*(1-abs(sign(subject-3)))) as sub3, 
       sum(number*(1-abs(sign(subject-4)))) as sub4, 
       sum(number*(1-abs(sign(subject-5)))) as sub5, 
       sum(number*(1-abs(sign(subject-6)))) as sub6 
from result GROUP BY student_id) m
where class_id = '7'

Answer 2

您还需要按class_id进行分组

SELECT * FROM ( 
select student_id, class_id,  
       sum(number*(1-abs(sign(subject-1)))) as sub1,  
       sum(number*(1-abs(sign(subject-2)))) as sub2,  
       sum(number*(1-abs(sign(subject-3)))) as sub3,  
       sum(number*(1-abs(sign(subject-4)))) as sub4,  
       sum(number*(1-abs(sign(subject-5)))) as sub5,  
       sum(number*(1-abs(sign(subject-6)))) as sub6  
from result GROUP BY student_id,class_id) m 
where class_id = '7'

Mysql数据透视表与where子句

2 个答案: