Question

我遇到了麻烦，需要一些帮助才能找到正确的SQL查询。到目前为止，这是我的代码：

SELECT firstname, lastname, date_of_birth 
  FROM `data` 
 WHERE firstname IN (SELECT firstname 
                       FROM `data` 
                      WHERE diagnosis_location = 'Mayo') 
   AND lastname IN (SELECT lastname 
                      FROM `data` 
                     WHERE diagnosis_location = 'Mayo') 
   AND date_of_birth IN (SELECT date_of_birth 
                           FROM `data` 
                          WHERE diagnosis_location = 'Mayo') 
   AND firstname IN (SELECT firstname 
                       FROM `data` 
                      WHERE diagnosis_location = 'Lahey') 
   AND lastname IN (SELECT lastname 
                      FROM `data` 
                     WHERE diagnosis_location = 'Lahey') 
   AND date_of_birth IN (SELECT date_of_birth 
                           FROM `data` 
                          WHERE diagnosis_location = 'Lahey')

是的，它是一个查询的怪物，可能并不是那么有效。但我要做的只是返回在'Mayo'位置和'Lahey'位置诊断出的所有患者的名字，姓氏和出生日期。此查询确实返回了这些患者，但它返回了相同确切数据的多行。

我怎么能限制它，所以修剪出相同结果的重复？

Answer 1

使用：

  SELECT firstname, lastname, date_of_birth 
    FROM `data`
   WHERE diagnosis_location IN ('Mayo', 'Lahey')
GROUP BY firstname, lastname, date_of_birth 
  HAVING COUNT(DISTINCT diagnosis_location) = 2

Answer 2

你应该考虑使用EXISTS来做这样的事情

也许尝试像

这样的东西

SELECT  DISTINCT
        firstname, 
        lastname, 
        date_of_birth 
FROM    `data` d
WHERE   EXISTS  (
                        SELECT  *
                        FROM    `data` dE
                        WHERE   d.firstname = dE.firstname
                        AND     d.lastname = dE.lastname
                        AND     d.date_of_birth = dE.date_of_birth
                        AND     diagnosis_location ='Mayo'
                )
AND     EXISTS  (
                        SELECT  *
                        FROM    `data` dE
                        WHERE   d.firstname = dE.firstname
                        AND     d.lastname = dE.lastname
                        AND     d.date_of_birth = dE.date_of_birth
                        AND     diagnosis_location = 'Lahey'
                )

Answer 3

试试这个：

 select `firstname`, `lastname`, `date_of_birth` 
    from `data`
   where `diagnosis_location`='Mayo' or  `diagnosis_location`='Lahey'
group by `firstname`, `lastname`, `date_of_birth` 
  having count(`diagnosis_location`) = 2

需要帮助在mySQL中返回独特的结果

3 个答案: