本文實(shí)例講述了MongoDB多表關(guān)聯(lián)查詢操作。分享給大家供大家參考，具體如下：
Mongoose的多表關(guān)聯(lián)查詢
首先，我們回憶一下，MySQL多表關(guān)聯(lián)查詢的語句：
student表：
calss表：
通過student的classId關(guān)聯(lián)進(jìn)行查詢學(xué)生名稱，班級(jí)的數(shù)據(jù)：
SELECT student.name,student.age,class.name FROM student,class WHERE student.classId = class.id
Mongoose多表聯(lián)合查詢(還是以眾所周知的學(xué)生、班級(jí)作為實(shí)例)
· 表結(jié)構(gòu)的定義(schemas目錄下)
1. student表(student.js)
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var mongoose = require('mongoose');var Schema = mongoose.Schema;/*定義數(shù)據(jù)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() } } /*更新時(shí)間的*/});module.exports = StudentSchema; |
2. class表(class.js)
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var mongoose = require('mongoose');var Schema = mongoose.Schema;/*定義數(shù)據(jù)模式*/var ClassSchema = new mongoose.Schema({ name: String, meta: { createAt: { type: Date, default: Date.now() }, updateAt: { type: Date, default: Date.now() } } /*更新時(shí)間的*/});module.exports = ClassSchema; |
· 生成Model（model目錄下）
1. student Model（student.js）
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var mongoose = require('mongoose');var StudentSchema = require('../schemas/student');/*通過model編譯模式為模型*/var Student = mongoose.model('student', StudentSchema);/*導(dǎo)出Student模型 模塊*/module.exports = Student; |
2. class Model（class.js）
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var mongoose = require('mongoose');var ClassSchema = require('../schemas/class');/*通過model編譯模式為模型*/var Class = mongoose.model('class', ClassSchema);/*導(dǎo)出Class模型 模塊*/module.exports = Class; |
· Model進(jìn)行數(shù)據(jù)的查詢操作
1. 將靜態(tài)類的方法加到Model的編譯中
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StudentSchema.static = { fetch: function(cb){ return this .find({}) .sort('meta.updateAt') //按更新的時(shí)間排序 }} |
2. 將靜態(tài)類方法加到Model中
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StudentSchema.static('fetch', function(cb){ return this .find({}, cb) .sort('meta.updateAt')}) |
3. 直接調(diào)用model的find()方法
查詢的結(jié)果均為：
[
{
_id: '5a05222f583e5720b8660191',
name: '張三',
age: 18,
number: 11,
classId: '5a0036512b740f32e4371e66'
},
{
_id: '5a05222f583e5720b8660091',
name: '李四',
age: 19,
number: 11,
classId: '5a0036512b740f32e1371e66'
},
{
_id: '5a05222f583e5720b18660191',
name: '趙五',
age: 17,
number: 11,
classId: '5a0036512b7420f32e4371e66'
}
]
· 多表聯(lián)合查詢（學(xué)生對(duì)應(yīng)班級(jí)）
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StudentSchema.static = { findStudentWithClass: function (cb) { return this .find({}) .populate('classId')//注意這是聯(lián)合查詢的關(guān)鍵 .sort('meta.updateAt') .exec(cb) }} |
查詢結(jié)果：
[
{
_id: '5a05222f583e5720b8660191',
name: '張三',
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: '趙五',
age: 18,
number: 11,
classId: {
_id: '5a0036512b7420f32e4371e66',
name: '一年2班'
}
}
]
· 由上面的實(shí)例可知，mongoose的多表聯(lián)合查詢的關(guān)鍵：
1. 數(shù)據(jù)模式結(jié)構(gòu)定義需要利用關(guān)鍵字ref定義關(guān)聯(lián)
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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 ); |
希望本文所述對(duì)大家MongoDB數(shù)據(jù)庫程序設(shè)計(jì)有所幫助。
原文鏈接：https://blog.csdn.net/WaterSprite_ct/article/details/78500997
