加入如果存在于MySQL查询中

Question

我正在运行一份报告，将委员会成员的信息导出到Excel电子表格中。

这是我的疑问：

SELECT membership_organization.name AS Firm, 
membership_individual.first AS FirstName, 
membership_individual.middle AS MiddleName, 
membership_individual.last AS LastName, 
membership_individual.email AS Email, 
membership_individual.phone AS Phone, 
membership_location.addr1 AS Address1, 
membership_location.addr2 AS Address2, 
membership_location.city AS City, 
membership_location.state AS State, 
membership_location.zipcode AS Zip 
FROM membership_individual 
JOIN membership_organization ON membership_individual.org_name_id = membership_organization.id 
JOIN membership_location ON membership_individual.location_id = membership_location.id 
WHERE membership_individual.id IN ({list if ids}) 
ORDER BY LastName

问题是某些成员没有设置位置ID，或者设置为0，因此这些成员不会显示在报告中。

有没有办法让我有资格获得位置JOIN？如果成员位置ID存在，请拉取信息，如果没有显示可用的信息。

Answer 1

将JOIN更改为LEFT JOIN s。您将从与where子句匹配的membership_individual获取所有记录，并为行不匹配的其他表获取NULL值。

Answer 2

使用LEFT OUTER JOIN：

SELECT membership_organization.name AS Firm, 
membership_individual.first AS FirstName, 
membership_individual.middle AS MiddleName, 
membership_individual.last AS LastName, 
membership_individual.email AS Email, 
membership_individual.phone AS Phone, 
membership_location.addr1 AS Address1, 
membership_location.addr2 AS Address2, 
membership_location.city AS City, 
membership_location.state AS State, 
membership_location.zipcode AS Zip 
FROM membership_individual 
JOIN membership_organization ON membership_individual.org_name_id = membership_organization.id 
LEFT OUTER JOIN membership_location ON membership_individual.location_id = membership_location.id 
WHERE membership_individual.id IN ({list if ids}) 
ORDER BY LastName

Answer 3

尝试使用

LEFT JOIN membership_location ON membership_individual.location_id = membership_location.id 

而不是你的变种..

Answer 4

使用左连接，意味着您的查询将变为

SELECT membership_organization.name AS Firm, 
membership_individual.first AS FirstName, 
membership_individual.middle AS MiddleName, 
membership_individual.last AS LastName, 
membership_individual.email AS Email, 
membership_individual.phone AS Phone, 
membership_location.addr1 AS Address1, 
membership_location.addr2 AS Address2, 
membership_location.city AS City, 
membership_location.state AS State, 
membership_location.zipcode AS Zip 
FROM membership_individual 
JOIN membership_organization ON membership_individual.org_name_id = membership_organization.id 
LEFT JOIN membership_location ON membership_individual.location_id = membership_location.id 
WHERE membership_individual.id IN ({list if ids}) 
ORDER BY LastName

您将获得所有成员的数据，甚至是位置表中没有行的成员。