Question

这里有两张表，即租金和student_hostel。租金表如下所示

    id   date      stud_id  paid    balance

    18  10-2016       94    15000   15000
    19  10-2016       94    10000   5000
    20  10-2016       96    25000   5000
    21  10-2016       96    5000    0

我的student_hostel表看起来像这样..

     id   first_name  last_name    stud_id     admit_date   hostel   class  room bed status

     94     ss        ff          PHBH00094     01-10-2016   12        16   115  501A    P
     96    maltu      uv          PHBH00096     01-10-2016   12        16   115  501C    p

为了获得最后插入的stud_id的余额，我使用了这样的代码，

public function rent_outstanding($hos,$dt)
{
    $sql = "select s.stud_id ,s.admit_date ,s.class,first_name,sum(paid) as rt_paid,balance,rt.stud_id 
            from student_hostel s, rent rt  where s.id=rt.stud_id and hostel=? and rt.date=? 
            and rt.id = (select max(id) from rent r where r.stud_id = rt.stud_id and r.date='$dt') 
            and status!= 'G' and status!= 'R'  GROUP BY rt.stud_id";
    $query=$this->db->query($sql, array($hos, $dt));
    return $query;
}

我面临的问题是我无法将相同stud_id的付费列下的值相加。我得到的输出是这样的

SI.No   STUDENT ID   NAME    RENT    PAID    BALANCE
 1      PHBH00094     Ss    30000    10000    5000  
 2      PHBH00096    Maltu  30000     5000      0

我需要得到的所需输出就像这样

SI.No   STUDENT ID   NAME    RENT    PAID    BALANCE
 1      PHBH00094     Ss    30000   25000     5000  
 2      PHBH00096    Maltu  30000   30000       0

Answer 1

您最终解决的问题是：

select s.stud_id ,s.admit_date ,s.class,first_name,sum(paid) as rt_paid, 
(select r.balance from rent r where r.stud_id = rt.stud_id and r.date='$dt' order by r.id desc limit 1) as balance ,rt.stud_id 
from student_hostel s join rent rt  on s.id=rt.stud_id where hostel=? and rt.date=? 
and status!= 'G' and status!= 'R'  GROUP BY s.stud_id

我已在您现有的查询rt.id = (select max(id) from rent r where r.stud_id = rt.stud_id and r.date='$dt')

中删除了这一行

您的(select max(id) from rent r where r.stud_id = rt.stud_id and r.date='$dt')表示始终只获得最后一行rt.id，例如19 (for PHBH00094)或21 (for PHBH00096)。这就是为什么你最后一次计算的原因。

从表中获取数据

1 个答案: