Question

我有两张桌子

1) students
2) fees_paid

学生表如下

id              Name
 1              xxxxxx
 2              yyyyyy
 3              zzzzzz

fees_paid如下

id    student_id           date            fees_paid
1      1                02-01-2015             250
2      1                05-01-2015             500
3      2                07-01-2015             400
4      1                06-02-2015             100
5      2                08-02-2015             200
6      3                04-05-2015             1000

我需要一个结果表，如下所示

Name         Jan       Feb     Mar    April     May


xxxxxx      750       100       0        0       0
yyyyyy      400       200       0        0       0
zzzzzz      0         0         0        0      1000

如何编写mysql查询以获取上述结果集

Answer 1

试试这个：

SELECT
    s.name,
    sum(case when month(f.date) = '01' then f.fees_paid else 0 end) as 'Jan',
    sum(case when month(f.date) = '02' then f.fees_paid else 0 end) as 'Feb',
    sum(case when month(f.date) = '03' then f.fees_paid else 0 end) as 'Mar',
    sum(case when month(f.date) = '04' then f.fees_paid else 0 end) as 'April',
    sum(case when month(f.date) = '05' then f.fees_paid else 0 end) as 'May'
FROM fees_paid f 
INNER JOIN students s ON s.id = f.student_id
GROUP BY s.id

Answer 2

试试这个，

$this->db->select('s.name,
sum(case when month(f.date) = '01' then f.fees_paid else 0 end) Jan,
sum(case when month(f.date) = '02' then f.fees_paid else 0 end) Feb,
sum(case when month(f.date) = '03' then f.fees_paid else 0 end) Mar,
sum(case when month(f.date) = '04' then f.fees_paid else 0 end) April,
sum(case when month(f.date) = '05' then f.fees_paid else 0 end) May');
$this->db->from('fees_paid');
$this->db->join('student', 'student.id = fees_paid.id', 'left');
$this->db->group_by("s.id"); 

$query = $this->db->get();

如何编写mysql查询以获得以下结果

2 个答案: