父where子句中的Mysql引用子查询结果

在我们学校，当一个学生表现良好时，他们会得到一个虚拟的英镑（或美元），它存储在一个数据库中

这是我的疑问：

SELECT s.chosen_name, s.chosen_surname, s.regId, s.admission_number, 
    (
        SELECT SUM(a.pounds_amount) 
        FROM tbl_pounds_log a 
        WHERE a.student_id=l.student_id
    ) AS total_pounds, 
    (
        SELECT SUM(b.pounds_amount) 
        FROM tbl_pounds_log b 
        WHERE b.student_id=l.student_id 
        AND b.staff_id=:staffId 
        AND b.action_timestamp>(UNIX_TIMESTAMP()-3600) 
    ) AS available_pounds 
FROM TBL_student s 
LEFT JOIN tbl_pounds_log l 
    ON l.student_id=s.admission_number 
WHERE ((s.chosen_name LIKE :termOne AND s.chosen_surname LIKE :termTwo) 
        OR (s.chosen_name LIKE :termThree AND s.chosen_surname LIKE :termFour))
    AND (total_pounds>=:lowerPoundLimit 
        AND total_pounds<=:upperPoundLimit) 
GROUP BY s.admission_number 
ORDER BY s.chosen_surname ASC, s.chosen_name ASC  
LIMIT 0,10

有人知道这个问题的解决办法吗

谢谢

---

Phil

试图避免子查询可能是“真正的”解决方案（可能会连接表并按结果分组）

---

无论如何，由于您不能在WHERE子句中引用“total_pounds”，因此一个简单的解决方案是重复子查询。这很难看，但可能查询优化器和/或服务器缓存（如果启用）会避免每个子查询执行2次…

尝试避免子查询可能是“真正的”解决方案（可能会连接表并按结果分组）

---

无论如何，由于您不能在WHERE子句中引用“total_pounds”，因此一个简单的解决方案是重复子查询。这很难看，但可能查询优化器和/或服务器的缓存（如果启用）会避免每个子查询执行2次…

问题是，在计算

WHERE

子句时，别名还不可用。应该通过将子查询从

SELECT

子句移动到

JOIN

子句来解决此问题，如下所示：

SELECT s.chosen_name, s.chosen_surname, s.regId, s.admission_number, 
       total_pounds.pound_amount as total_pounds,
       available_pounds.pound_amount as available_pounds
FROM TBL_student s
LEFT JOIN
  (SELECT student_id, SUM(pounds_amount) AS pound_amount 
   FROM tbl_pounds_log
   GROUP BY student_id) AS total_pounds
ON total_pounds.student_id = s.admission_number 
LEFT JOIN
  (SELECT student_id, SUM(b.pounds_amount) AS pound_amount
   FROM tbl_pounds_log 
   WHERE b.staff_id=:staffId 
   AND b.action_timestamp>(UNIX_TIMESTAMP()-3600)
   GROUP BY student_id) as available_pounds  
ON available_pounds.student_id = s.admission_number
WHERE ((s.chosen_name LIKE :termOne AND s.chosen_surname LIKE :termTwo) 
        OR (s.chosen_name LIKE :termThree AND s.chosen_surname LIKE :termFour))
    AND (total_pounds.pound_amount >= :lowerPoundLimit 
        AND total_pounds.pound_amount <= :upperPoundLimit) 
GROUP BY s.admission_number 
ORDER BY s.chosen_surname ASC, s.chosen_name ASC  
LIMIT 0,10

---

问题是，在计算

WHERE

子句时，别名还不可用。应该通过将子查询从

SELECT

子句移动到

JOIN

子句来解决此问题，如下所示：

SELECT s.chosen_name, s.chosen_surname, s.regId, s.admission_number, 
       total_pounds.pound_amount as total_pounds,
       available_pounds.pound_amount as available_pounds
FROM TBL_student s
LEFT JOIN
  (SELECT student_id, SUM(pounds_amount) AS pound_amount 
   FROM tbl_pounds_log
   GROUP BY student_id) AS total_pounds
ON total_pounds.student_id = s.admission_number 
LEFT JOIN
  (SELECT student_id, SUM(b.pounds_amount) AS pound_amount
   FROM tbl_pounds_log 
   WHERE b.staff_id=:staffId 
   AND b.action_timestamp>(UNIX_TIMESTAMP()-3600)
   GROUP BY student_id) as available_pounds  
ON available_pounds.student_id = s.admission_number
WHERE ((s.chosen_name LIKE :termOne AND s.chosen_surname LIKE :termTwo) 
        OR (s.chosen_name LIKE :termThree AND s.chosen_surname LIKE :termFour))
    AND (total_pounds.pound_amount >= :lowerPoundLimit 
        AND total_pounds.pound_amount <= :upperPoundLimit) 
GROUP BY s.admission_number 
ORDER BY s.chosen_surname ASC, s.chosen_name ASC  
LIMIT 0,10

---

这两个查询在返回的结果方面有什么不同吗？再次感谢：）我认为他们应该返回相同的结果，但由于缺少数据，我无法对他们进行测试。再次感谢，我已经对底部的一个进行了测试，结果与预期的一样：）两个查询之间在返回的结果方面是否有任何差异？再次感谢：）我认为他们应该返回相同的结果，但由于缺乏数据，我无法对他们进行测试。再次感谢，我已经对底部的一个进行了测试，结果与预期的一样：）

SELECT s.chosen_name, s.chosen_surname, s.regId, s.admission_number, 
       total_pounds.pound_amount as total_pounds,
       available_pounds.pound_amount as available_pounds
FROM TBL_student s
LEFT JOIN
  (SELECT student_id, SUM(pounds_amount) AS pound_amount 
   FROM tbl_pounds_log
   GROUP BY student_id) AS total_pounds
ON total_pounds.student_id = s.admission_number 
LEFT JOIN
  (SELECT student_id, SUM(b.pounds_amount) AS pound_amount
   FROM tbl_pounds_log 
   WHERE b.staff_id=:staffId 
   AND b.action_timestamp>(UNIX_TIMESTAMP()-3600)
   GROUP BY student_id) as available_pounds  
ON available_pounds.student_id = s.admission_number
WHERE ((s.chosen_name LIKE :termOne AND s.chosen_surname LIKE :termTwo) 
        OR (s.chosen_name LIKE :termThree AND s.chosen_surname LIKE :termFour))
    AND (total_pounds.pound_amount >= :lowerPoundLimit 
        AND total_pounds.pound_amount <= :upperPoundLimit) 
GROUP BY s.admission_number 
ORDER BY s.chosen_surname ASC, s.chosen_name ASC  
LIMIT 0,10

SELECT s.chosen_name, s.chosen_surname, s.regId, s.admission_number,
       SUM(tp.pounds_amount) AS total_pounds
       SUM(ap.pounds_amount) AS available pounds
FROM tbl_students s
LEFT JOIN tbl_pounds_log tp
ON tp.student_id = s.admission_number
LEFT JOIN tbl_pounds_log ap
ON ap.student_id = tp.student_id
AND ap.staff_id = tp.staff_id
AND ap.staff_id = :staffId
AND ap.action_timestamp = tp.action_timestamp
AND ap.action_timestamp > (UNIX_TIMESTAMP()-3600)
WHERE s.chosen_name LIKE :termOne AND s.chosen_surname LIKE :termTwo
OR s.chosen_name LIKE :termThree AND s.chosen_surname LIKE :termFour
GROUP BY s.admission_number, s.name, s.regId, s.admission_number
HAVING SUM(tp.pounds_amount) BETWEEN upperPoundLimit AND lowerPoundLimit
ORDER BY s.chosen_surname, s.chosen_name
LIMIT 0,10