如果后续匹配不存在，则 SQL 选择行 [关闭]答案

【问题标题】：SQL select rows if subsequent match not exists [closed]如果后续匹配不存在，则 SQL 选择行 [关闭]
【发布时间】：2021-02-17 22:38:31
【问题描述】：

我有一个示例 SQL 查询，它返回如下结果：

CLIENT	REQUESTDATE	COUNTRY	ARRIVAL	STATUS
A	2019-04-01	Australia	2020-03-15	Closed
B	2020-02-12	Germany	2021-05-03	Closed
C	2019-10-21	Italy	2020-03-06	Closed
D	2019-09-11	United Kingdom	2020-03-01	Closed
EEE	2020-01-30	Netherlands	2020-03-23	Sold
F	2019-06-10	South Africa	2020-02-15	Closed
G	2019-08-26	Luxembourg	2020-08-25	Closed
HHH	2019-04-09	India	2021-03-21	Sold
HHH	2019-10-10	India	2020-10-12	Closed
HHH	2020-10-14	India	2021-09-12	Follow up

这是 SQL 查询：

SELECT
Clients.name as CLIENT,
Requests.requestDate AS REQUESTDATE,
Countries.name as COUNTRY, 
Requests.arrivalDate AS ARRIVAL,
RequestStatus.name as STATUS 
FROM Clients 
JOIN Countries ON Countries.id=Clients.countryId 
JOIN RequestClientEvent ON RequestClientEvent.clientId=Clients.id 
JOIN Requests ON Requests.requestClientEventId=RequestClientEvent.id 
JOIN RequestStatus ON RequestStatus.id=Requests.requestStatusId 
AND Requests.arrivalDate >= '2020-01-01' 
GROUP BY Clients.name, RequestStatus.id
ORDER BY Clients.name, Requests.requestDate, RequestStatus.id ASC
LIMIT 10

是否可以只返回状态为“已售出”的客户，之后没有同一客户的任何后续记录（按请求日期）。

这样查询例如根据上表返回客户端“EEE”。

【问题讨论】：

是的，有可能

标签： mysql sql select

【解决方案1】：

使用别名您需要加入同一个请求表两次，一个closedR 包含已关闭的请求，而subsequentR 包含更大日期的任何内容。

SELECT ...
FROM Clients C
JOIN Request closedR
  ON closedR.requestClientEventId=C.id
     AND closedR.status="Closed"
LEFT JOIN Request subsequentR
  ON subsequentR.requestClientEventId = C.id
     AND subsequentR.requestDate > closedR.requestDate
WHERE subsequentR.id IS NULL

LEFT JOIN / WHERE .. IS NULL 允许您找到任何不匹配的内容。

【讨论】：