本文实例讲述了MongoDB多表关联查询操作。分享给大家供大家参考,具体如下:
Mongoose的多表关联查询
首先,我们回忆一下,MySQL多表关联查询的语句:
student表:
calss表:
通过student的classId关联进行查询学生名称,班级的数据:
SELECT student.name,student.age,class.name FROM student,class WHERE student.classId = class.id
Mongoose多表联合查询(还是以众所周知的学生、班级作为实例)
· 表结构的定义(schemas目录下)
1. student表(student.js)
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var mongoose = require( 'mongoose' ); var Schema = mongoose.Schema; /*定义数据模式*/ var StudentSchema = new mongoose.Schema({ name: String, calssId: { type: Schema.Types.objectId, ref: 'class' }, age: Number, number: Number, meta: { createAt: { type: Date, default : Date.now() }, updateAt: { type: Date, default : Date.now() } } /*更新时间的*/ }); module.exports = StudentSchema; |
2. class表(class.js)
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var mongoose = require( 'mongoose' ); var Schema = mongoose.Schema; /*定义数据模式*/ var ClassSchema = new mongoose.Schema({ name: String, meta: { createAt: { type: Date, default : Date.now() }, updateAt: { type: Date, default : Date.now() } } /*更新时间的*/ }); module.exports = ClassSchema; |
· 生成Model(model目录下)
1. student Model(student.js)
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var mongoose = require( 'mongoose' ); var StudentSchema = require( '../schemas/student' ); /*通过model编译模式为模型*/ var Student = mongoose.model( 'student' , StudentSchema); /*导出Student模型 模块*/ module.exports = Student; |
2. class Model(class.js)
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var mongoose = require( 'mongoose' ); var ClassSchema = require( '../schemas/class' ); /*通过model编译模式为模型*/ var Class = mongoose.model( 'class' , ClassSchema); /*导出Class模型 模块*/ module.exports = Class; |
· Model进行数据的查询操作
1. 将静态类的方法加到Model的编译中
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StudentSchema.static = { fetch: function (cb){ return this .find({}) .sort( 'meta.updateAt' ) //按更新的时间排序 } } |
2. 将静态类方法加到Model中
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StudentSchema.static( 'fetch' , function (cb){ return this .find({}, cb) .sort( 'meta.updateAt' ) }) |
3. 直接调用model的find()方法
查询的结果均为:
[
{
_id: '5a05222f583e5720b8660191',
name: '张三',
age: 18,
number: 11,
classId: '5a0036512b740f32e4371e66'
},
{
_id: '5a05222f583e5720b8660091',
name: '李四',
age: 19,
number: 11,
classId: '5a0036512b740f32e1371e66'
},
{
_id: '5a05222f583e5720b18660191',
name: '赵五',
age: 17,
number: 11,
classId: '5a0036512b7420f32e4371e66'
}
]
· 多表联合查询(学生对应班级)
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StudentSchema.static = { findStudentWithClass: function (cb) { return this .find({}) .populate( 'classId' ) //注意这是联合查询的关键 .sort( 'meta.updateAt' ) .exec(cb) } } |
查询结果:
[
{
_id: '5a05222f583e5720b8660191',
name: '张三',
age: 18,
number: 11,
classId: {
_id: '5a0036512b740f32e4371e66',
name: '一年1班'
}
},
{
_id: '5a05222f583e5720b8660091',
name: '李四',
age: 18,
number: 11,
classId: {
_id: '5a0036512b740f32e1371e66',
name: '二年2班'
}
},
{
_id: '5a05222f583e5720b18660191',
name: '赵五',
age: 18,
number: 11,
classId: {
_id: '5a0036512b7420f32e4371e66',
name: '一年2班'
}
}
]
· 由上面的实例可知,mongoose的多表联合查询的关键:
1. 数据模式结构定义需要利用关键字ref定义关联
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var Schema = new mongoose.Schema({ field: { type: mongoose.Schema.Type.ObjectId, ref: 'model' } }); Schema.static = { fetch: function (cb){ return this .find({}) .populate( 'field' ) .exec(cb) } } var Model = mongoose.Model( 'model' ,Schema ); |
希望本文所述对大家MongoDB数据库程序设计有所帮助。
原文链接:https://blog.csdn.net/WaterSprite_ct/article/details/78500997