[英]The surprising problem in Many-to-many associations using Sequelize
I created three tables posts, tags, and post_tags.我创建了三个表 post、tags 和 post_tags。 Each Post belongs to many Tags through PostTags and each Tags belongs to many Post through PostTag.
每个帖子通过 PostTags 属于许多标签,每个标签通过 PostTag 属于许多帖子。 The surprising problem is when I sort
posts.id
as DESC
the Tags will be empty and the join query result doesn't return any tag.令人惊讶的问题是,当我将
posts.id
排序为DESC
,标签将为空并且连接查询结果不返回任何标签。 but when I sort id
as ASC
the tags will be shown in the result JSON.但是当我将
id
排序为ASC
,标签将显示在结果 JSON 中。 Some of the posts don't have tag.有些帖子没有标签。 I don't know why this problem is there.
我不知道为什么会出现这个问题。 If knowing the type of database helps to fix the problem, I use Postgresql.
如果知道数据库的类型有助于解决问题,我使用 Postgresql。
Models structures are:模型结构是:
// Posts Model
const posts = (sequelize, DataTypes) => {
const posts = sequelize.define(
"posts",
{
userId: DataTypes.INTEGER,
title: DataTypes.STRING,
},
{
tableName: "posts",
timestamps: true,
paranoid: true
}
);
// Relations
posts.associate = (models) => {
posts.belongsToMany(models.tags, {
through: 'postTags',
as: 'tags',
foreignKey: 'postId',
otherKey: 'tagId'
});
}
return posts;
};
// Tags Model
const tags = sequelize.define(
"tags",
{
title: DataTypes.STRING
},
{
tableName: "tags",
timestamps: true,
paranoid: true
}
);
// Relations
tags.associate = (models) => {
tags.belongsToMany(models.posts, {
through: 'postTags',
as: 'posts',
foreignKey: 'tagId',
otherKey: 'postId'
});
}
return tags;
};
// PostTags Model
const post_tags = (sequelize, DataTypes) => {
const post_tags = sequelize.define(
"postTags",
{
postId: DataTypes.INTEGER,
tagId: DataTypes.INTEGER
},
{
tableName: "post_tags",
timestamps: true,
paranoid: true
}
);
return post_tags;
};
And I selected rows by these options:我通过这些选项选择了行:
const posts = models.posts.findAll({
attributes: [
'id',
'title'
],
include: [
{
model: models.tags,
as: 'tags',
required: false,
attributes: [
'id',
'title'
],
through: {
model: models.postTags,
as: 'postTags',
attributes: [
'postId',
'tagId'
]
}
}
],
order: [['id', 'desc']]
});
Are you logging your sequelize queries to console?您是否将 sequelize 查询记录到控制台? I have never had any issue with this, but you may be getting something you don't expect in your query... paste them both into your question if you log them...
我从来没有遇到过任何问题,但是您可能会在查询中得到一些您不期望的东西……如果您记录它们,请将它们粘贴到您的问题中……
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