Question

我已经建立了这样的查询：

        SELECT 
           c.*,
           (SELECT COUNT(cursus_id) FROM cursusdienst_bestellingen where cursus_id = c.id AND datum_afhaling IS  NULL AND datum_verwijderd IS NULL AND studentid = '$studentid') as besteld,
           (SELECT COUNT(cursus_id) FROM cursusdienst_bestellingen where cursus_id = c.id AND datum_afhaling IS NOT NULL AND datum_verwijderd IS NULL AND datum_afgehaald IS NULL AND studentid = '$studentid') as afhalen,
           (SELECT datum_afhaling + INTERVAL 14 DAY FROM cursusdienst_bestellingen where cursus_id = c.id AND datum_afhaling IS NOT NULL AND datum_verwijderd IS NULL AND datum_afgehaald IS NULL AND studentid = '$studentid') as datum_afhaling,
           (SELECT COUNT(cursus_id) FROM cursusdienst_bestellingen where cursus_id = c.id AND datum_afgehaald IS NOT NULL AND datum_verwijderd IS NULL AND cb.studentid = '$studentid') as afgehaald
        FROM 
           cursusdienst c
        LEFT JOIN
           cursusdienst_bestellingen cb
        ON
           cb.cursus_id = c.id    
        WHERE 
           c.studierichting = '1ste Bachelor'
        ORDER BY 
           c.artikel asc, cb.studentid

这是学生和课程的注册/订购系统。有很多学生使用这个系统。学生必须先注册才能订购课程。我的查询存在问题，因为我看到同一个列表中每个学生的课程。这里有一个例子：

Checkbox         Course              Price     Status
Checkbox         Course 1            12.00     Ordered
Checkbox         Course 1            12.00     Ordered
Checkbox         Course 2            25.50     Ready to deliver
Checkbox         Course 3            15.00

如您所见，查询向我显示了2名学生的所有课程信息（仅作为示例）他们已登录并订购了课程。第一个学生订购了Course 1 en 2，第二个学生只订购了Course 1。如果我以学生身份登录，我只想看到我订购的课程的状态，但我也看到其他课程（没有任何状态，如课程3），所以我可以订购相同形式的其他课程。不想看到的是其他人的订单！

所以我想只看到这个，如果我作为一名学生，订购了课程1和2.课程3也在列表中，因为我现在可以订购，但我之前没有订购（所以它没有状态）：

Checkbox         Course              Price     Status
Checkbox         Course 1            12.00     Ordered
Checkbox         Course 2            25.50     Ready to deliver
Checkbox         Course 3            15.00

如果我添加＆＃34;并且cb.studentid =＆＃39; $ studentid＆＃39;＆＃34;在那里我只看到我订购的课程，而不是我没有订购的其他课程。

编辑:(感谢SunKnight0）设置＆＃34; AND cb.studentid =＆＃39; $ studentid＆＃39;＆＃34;在ON部分而不是在WHERE部分！因此，工作代码如下所示：

        SELECT 
           c.*,
           (SELECT COUNT(cursus_id) FROM cursusdienst_bestellingen where cursus_id = c.id AND datum_afhaling IS  NULL AND datum_verwijderd IS NULL AND studentid = '$studentid') as besteld,
           (SELECT COUNT(cursus_id) FROM cursusdienst_bestellingen where cursus_id = c.id AND datum_afhaling IS NOT NULL AND datum_verwijderd IS NULL AND datum_afgehaald IS NULL AND studentid = '$studentid') as afhalen,
           (SELECT datum_afhaling + INTERVAL 14 DAY FROM cursusdienst_bestellingen where cursus_id = c.id AND datum_afhaling IS NOT NULL AND datum_verwijderd IS NULL AND datum_afgehaald IS NULL AND studentid = '$studentid') as datum_afhaling,
           (SELECT COUNT(cursus_id) FROM cursusdienst_bestellingen where cursus_id = c.id AND datum_afgehaald IS NOT NULL AND datum_verwijderd IS NULL AND cb.studentid = '$studentid') as afgehaald
        FROM 
           cursusdienst c
        LEFT JOIN
           cursusdienst_bestellingen cb
        ON
           cb.cursus_id = c.id AND cb.student_id = '$studentid'  
        WHERE 
           c.studierichting = '1ste Bachelor'
        ORDER BY 
           c.artikel asc, cb.studentid

Answer 1

SELECT 
   c.*,
   (SELECT COUNT(cursus_id) FROM cursusdienst_bestellingen where cursus_id = c.id AND datum_afhaling IS  NULL AND datum_verwijderd IS NULL AND studentid = '$studentid') as besteld,
   (SELECT COUNT(cursus_id) FROM cursusdienst_bestellingen where cursus_id = c.id AND datum_afhaling IS NOT NULL AND datum_verwijderd IS NULL AND datum_afgehaald IS NULL AND studentid = '$studentid') as afhalen,
   (SELECT datum_afhaling + INTERVAL 14 DAY FROM cursusdienst_bestellingen where cursus_id = c.id AND datum_afhaling IS NOT NULL AND datum_verwijderd IS NULL AND datum_afgehaald IS NULL AND studentid = '$studentid') as datum_afhaling,
   (SELECT COUNT(cursus_id) FROM cursusdienst_bestellingen where cursus_id = c.id AND datum_afgehaald IS NOT NULL AND datum_verwijderd IS NULL AND cb.studentid = '$studentid') as afgehaald
FROM 
   cursusdienst c
LEFT JOIN
   cursusdienst_bestellingen cb
ON
   cb.cursus_id = c.id AND cb.studentid = '$studentid'
WHERE 
   c.studierichting = '1ste Bachelor'
ORDER BY 
   c.artikel asc, cb.studentid

查询未显示正确的结果

1 个答案: