Question

我有一个SQL查询，其中SUM聚合函数只返回所有值的两倍。我完全不明白，它是如何发生的。这是查询

 SELECT 
  st.id,
  u.id AS user_id,
  st.student_code,
  spd.first_name,
  spd.middle_name,
  spd.last_name,
  spd.birth_date,
  classes.`class_name`,
  sections.`section_name`,
  sed.`roll_no`,
  sgd.first_name AS gardian_first_name,
  sgd.middle_name AS gardian_middle_name,
  sgd.last_name AS gardian_last_name,
  sgd.contact_no,
  SUM(sfd.`final_fee`) AS total_calculated_fee,
  SUM(sfd.`total_paid_amount`) AS total_paid_amount,
  SUM(sfd.`total_due_amount`) AS total_due_amount 
FROM
  students st 
  LEFT JOIN users u 
    ON st.`id` = u.`student_id` 
  LEFT JOIN student_personal_details spd 
    ON st.`id` = spd.`student_id` 
  LEFT JOIN student_gardian_details sgd 
    ON st.`id` = sgd.`student_id` 
  LEFT JOIN student_education_details sed 
    ON st.`id` = sed.`student_id` 
  LEFT JOIN student_hostel_details shd 
    ON st.`id` = shd.`student_id` 

  LEFT JOIN classes 
    ON sed.`class_id` = classes.`class_id` 
  LEFT JOIN sections 
    ON sed.`section_id` = sections.`id` 
    LEFT JOIN student_fee_details sfd 
    ON st.`id` = sfd.`student_id` 
WHERE st.is_active = 1 AND st.`id` = 2
GROUP BY sfd.`student_id` 
LIMIT 0, 10

我在所有三个字段中都使用了distinct，但是中间的字段返回1/4值。任何人都可以帮助我

SUM返回具有多个左连接的double值

0 个答案: