Question

我试图找到一个既有失眠又感冒的人。

到目前为止我尝试过的代码是：

SELECT Patient.patientName, Patient.patientPNbr
FROM Patient
LEFT JOIN SuffersFrom
ON Patient.patientPNbr = SuffersFrom.patientPNbr
WHERE diseaseName = 'Insomnia'
AND diseaseName = 'Influenza'

你会如何找到这个人？

Answer 1

如果想要返回患有这两种疾病的患者，请尝试这样做

SELECT Patient.patientName, Patient.patientPNbr
FROM Patient
INNER JOIN SuffersFrom ON Patient.patientPNbr = SuffersFrom.patientPNbr
WHERE diseaseName IN ('Insomnia','Influenza')
GROUP BY Patient.patientName, Patient.patientPNbr
HAVING COUNT(diseaseName)>1

Answer 2

您需要多次使用SuffersFrom（每次检查疾病一次）。我会使用EXISTS子句。

SELECT SELECT Patient.patientName, Patient.patientPNbr
FROM Patient
--Check for Insomnia
WHERE EXISTS (SELECT 1
    FROM SuffersFrom
    WHERE Patient.patientPNbr = SuffersFrom.patientPNbr
    AND diseaseName = 'Insomnia')
--Check for Influenza
AND EXISTS (SELECT 1
    FROM SuffersFrom
    WHERE Patient.patientPNbr = SuffersFrom.patientPNbr
    AND diseaseName = 'Influenza')

Answer 3

使用以下查询加入...

       SELECT P.patientName, P.patientPNbr
       FROM Patient p
             INNER JOIN SuffersFrom s
                  ON p.patientPNbr = s.patientPNbr
             INNER JOIN SuffersFrom s1
                  ON s.patientPNbr = s1.patientPNbr   
        WHERE s.diseaseName = 'Insomnia'
               AND s1.diseaseName = 'Influenza'

如何让患有多种疾病的人

3 个答案: