mysql - 未正确加入

Question

我有以下查询，它从一系列表中获取一堆列

SELECT Events.eventID, Events.eventName, Organisations.organisationName, Events.eventCrewSize, Events.eventGuestSize, Events.eventDate, Events.eventTime, Boat.boatName, Address.addressNo, Address.addressStreet, Address.addressStreetType, Address.addressSuburb, Address.addressPostCode, Address.addressState 
FROM Events, Organisations, Boat, Address 
WHERE Events.eventOrganisation = Organisations.organisationID AND Events.eventBoatID = Boat.boatID AND Events.eventAddressID = Address.addressID AND Events.eventDate >= CURDATE();

我的问题是，并非所有事件都有组织，并且该列不会返回 NULL，而是不包含任何没有组织的事件。

我尝试从 where 子句中删除包含空行的组织部分，但它使用另一个事件的组织作为其值，而不是实际的空值。

我认为这是一个联接问题，但不确定如何相应地构建它。

Answer 1

您可以尝试使用左连接

SELECT Events.eventID, Events.eventName, Organisations.organisationName, Events.eventCrewSize, Events.eventGuestSize, Events.eventDate, Events.eventTime, Boat.boatName, Address.addressNo, Address.addressStreet, Address.addressStreetType, Address.addressSuburb, Address.addressPostCode, Address.addressState 
FROM Events 
LEFT JOIN Organisations on Events.eventOrganisation = Organisations.organisationID
LEFT JOIN Boat on Events.eventBoatID = Boat.boatID
LEFT JOIN Address on Events.eventAddressID = Address.addressID
WHERE Events.eventDate >= CURDATE();

不要忘记应用主键和外键/规范化之间的关系。您可以使用 NULLIF() 来避免空值