我想从数据库中获得4个不同类别的50个问题.我想要从4个不同类别中选择不同数量的问题;我的结果集必须包含第一类12个问题,第二类20个问题,第三类10和第四类8个问题.我的问题表中总共有50个问题. 我为此使用了 LIMIT 函数.但是当我有不止一列的时候,我很困惑.
I would like to get 50 questions from 4 different categories from the database. I want a different number of questions from each of the 4 different categories; my result set must contain first category 12 questions, second category 20 questions, third 10, and fourth category 8 questions. In total 50 question from my question table. I used the LIMIT function for this. But when I have more than one column, I'm confused.
这是我的桌子:
| category_id| question-text| Col3 | |------------|--------------|------| | 1 | sample | ieb | | 2 | sample | aem | | 3 | sample | atd | | 4 | sample | oui | | 1 | sample | ieb | | 2 | sample | aem | | 3 | sample | atd | | 4 | sample | oui | | 1 | sample | ieb | | 2 | sample | aem | | 3 | sample | atd | | 4 | sample | oui | | 1 | sample | ieb | | 2 | sample | aem | | 3 | sample | atd | | 4 | sample | oui |我需要这个结果: 类别1中有5个问题. 类别2中的3个问题. 类别3中的2个问题. 类别4中有7个问题.
And I need this result: 5 questions from category # 1. 3 questions from category # 2. 2 questions from category # 3. 7 questions from category # 4.
推荐答案您可以使用 UNION 查询可一次获得所有问题:
You can use a UNION query to get all your questions at once:
(SELECT * FROM question WHERE categori_id=1 ORDER BY RAND() LIMIT 12) UNION (SELECT * FROM question WHERE categori_id=2 ORDER BY RAND() LIMIT 20) UNION (SELECT * FROM question WHERE categori_id=3 ORDER BY RAND() LIMIT 10) UNION (SELECT * FROM question WHERE categori_id=4 ORDER BY RAND() LIMIT 8)更多推荐
如何通过在MySql上过滤多个列来限制多个数字?
发布评论