左排除加入续集

Question

我有两张表，其中一张表具有另一张表的 ID。1:1 关系。所以像

EventFeedback
    somePrimaryKey
    userEventID
UserEvent
    userEventID

Sequalize 的关系定义为

models.UserEvent.hasOne(models.EventFeedback, { foreignKey: 'userEventID' });

我需要的所有条目UserEvent没有一个条目EventFeedback，这是一个排他性的加入。从这篇文章中窃取图像，因为它们有很好的个人图像：

他们甚至给出了示例代码！

SELECT <select_list> 
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
WHERE B.Key IS NULL

我如何在续集中做到这一点？我是否只需要进行左连接并手动处理它？

Answer 1

You need to eager load EventFeedback when querying UserEvent and add proper where clause. You also need to define that EventFeedback is not required in the result so the query will generate LEFT JOIN instead INNER JOIN

UserEvent.all({
    include: [
        model: EventFeedback,
        required: false, // do not generate INNER JOIN
        attributes: [] // do not return any columns of the EventFeedback table
    ],
    where: sequelize.where(
        sequelize.col('EventFeedback.userEventID'),
        'IS',
        null
    )
}).then(userEvents => {
    // user events...
});

In the code above the sequelize is an instance of Sequelize with model defined in it. You can also refer to the documentation of sequelize.where() and sequelize.col() methods.