Question

我加入了一些表格，以便我有这样的结果表

<table border="1" style="border-collapse: collapse">
    <tr><th>ID</th><th>name</th><th>val</th></tr>
    
    <tr><td>1</td><td>n1</td><td>false</td></tr>
    <tr><td>1</td><td>n2</td><td>true</td></tr>
    <tr><td>1</td><td>n3</td><td>true</td></tr>

    <tr><td>2</td><td>n1</td><td>true</td></tr>
    <tr><td>2</td><td>n2</td><td>true</td></tr>
    <tr><td>2</td><td>n3</td><td>true</td></tr>

    <tr><td>3</td><td>n1</td><td>false</td></tr>
    <tr><td>3</td><td>n2</td><td>true</td></tr>
    <tr><td>3</td><td>n3</td><td>true</td></tr>
</table>

我需要获取ID，对于此ID n1 = true且n2 = true，因此从该表中只有ID 2才是正确的。如何针对非预定义的名称和值进行此类请求？

Answer 1

SELECT id FROM t
GROUP BY id
HAVING SUM(name='n1' AND val='true')>0
AND SUM(name='n2' AND val='true')>0

Answer 2

可能的解决方案是

select  distinct id
from    yourTable t1
join    yourTable t2
on      t1.id = t2.id
where   t1.name = n1 and t1.val = 'true' and
        t2.name = n2 and t2.val = 'true';

按连接表值选择

2 个答案: