[英]Sequelize.js,How to insert a model with one to many to many relationship
[英]sequelize.js consecutive many to many relationship
我有A,B和C類
A <-多對多-> B和B <-多對多-> C
對於單個A,我想查找與A相關的所有C。
如何編寫sequelize查詢,使其僅執行一個SQL調用?
多對多關系已經在sequelize中定義,例如,我已經可以執行a.getBs(),b.getCs()或c.getBs()
我顯然可以寫,
a.getBs()
.then(function(Bs) {
return foreach(Bs, function(b) {return b.getCs();})
})
.then(function() {
// flatten array of array of C here.
})
但是,這執行了太多的SQL請求。
另外,如果我有A數組怎么辦? 有沒有一種方法可以只執行一個SQL以返回{a1:[“ c1”,“ c2”],a2:[“ c2”,“ c99”] ...}的映射
SELECT A.name, C.name as anotherName
FROM A
LEFT JOIN A_B ON A.id = A_B.A_id
LEFT JOIN B ON A_B.B_id = B.id
LEFT JOIN B_C ON B.id = B_C.B_id
LEFT JOIN C ON C.id = B_C.C_id
GROUP BY name, anotherName
我認為這是我需要的SQL,不確定如何從續集生成它。
Sequelize主要使用包含和急切加載來加入關聯,因此您的查詢應如下所示:
A.findAll({
where: { etc... }
include: [
{
association: A.associations.B,
include: [
B.associations.C
]
}
],
}).then((results) => {
console.log(results[0].B[0].C[0]);
});
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