Question

我有下表：
的患者
ID
命名
diagnosis_id

我需要做的是让所有患有N最常见诊断的患者我使用这个查询什么都没得到：
SELECT name FROM patients WHERE diagnosis_id IN (SELECT TOP(5) COUNT(diagnosis_id) FROM patients GROUP BY diagnosis_id ORDER BY diagnosis_id)
如何解决？

Answer 1

SELECT name FROM patients
WHERE diagnosis_id IN
(
SELECT TOP(5) diagnosis_id FROM patients
GROUP BY diagnosis_id
ORDER BY COUNT(diagnosis_id) desc
)

Answer 2

这有几个问题：

首先，我recommend using a common table expression进行“前5”查找而不是子查询 - 对我来说，它使它更清晰一点，虽然这里没关系，但它可能会更好真实的工作情况。

但主要的问题是，您是按诊断ID而不是计数排序前5位查找。您需要改为ORDER BY COUNT(diagnosis_id)。

Answer 3

select p.name from patients p
inner join (
    select top 5 diagnosis_id, count(*) as diagnosis_count
    from patients
    group by diagnosis_id
    order by diagnosis_count) t on t.diagnosis_id = p.diagnosis_id

Answer 4

试试这个：

SELECT name FROM patients
WHERE diagnosis_id IN
(SELECT TOP(5) diagnosis_id FROM patients
GROUP BY diagnosis_id
ORDER BY COUNT(diagnosis_id))

SQL top + count（）混淆

4 个答案: