How to query multiple mongo collections in express?

2020-04-30T07:52:55+00:00

This article is good for understanding the relationships between multiple data collections in mongoDB. This article explains how one can handle one to many relations in mongoDB database and properly organize the collections in database.

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2020-05-06T08:18:47+00:00

There are three types of Model relationships between documents in mongoDB. Model one-to-one, one-to-many with embedded documents and one-to-many with document references. This article explains very well about using document references to create relationships between collections. One can have a more general look here: https://docs.mongodb.com/manual/tutorial/model-referenced-one-to-many-relationships-between-documents/

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	const express = require('express');
	const bodyParser = require('body-parser');
	const mongoose = require('mongoose');

	const app = express();


	mongoose.connect('mongodb://localhost:27017/Posts');

	app.use(bodyParser.urlencoded({ extended: true }));
	app.use(bodyParser.json());


	const authorRouter = require('./Views/author');
	const postRouter = require('./Views/posts');

	app.use('/api', authorRouter);
	app.use('/api', postRouter);

	const PORT = process.env.PORT \|\| 3000;

	app.listen(PORT, () => {
	console.log(`Application running on port ${PORT}`);
	});

	const mongoose = require('mongoose');

	const { Schema } = mongoose;

	const postModel = new Schema({
	title: String,
	author: {
	type: Schema.Types.ObjectId,
	ref: 'authors',
	},
	date: {
	type: Date,
	required: true,
	},
	});


	module.exports = mongoose.model('posts', postModel);


	const express = require('express');
	const postController = require('../controllers/post');

	const postRouter = express.Router();

	postRouter.param('id', postController.params);


	postRouter.route('/posts')
	.get(postController.get);

	postRouter.route('/posts/:id')
	.delete(postController.delete)
	.get(postController.getOne);

	postRouter.route('/author/:authorID/posts')
	.post(postController.post);

	postRouter.route('/authors/:authorId/posts/:postId')
	.put(postController.update);


	module.exports = postRouter;

	exports.post = async function (req, res) {
	const authorId = await req.params.authorID;
	const postObject = await req.body;
	const newPost = new PostModel(postObject);

	await AuthorModel.findOne({ _id: authorId }, async (err, foundAuthor) => {
	if (!foundAuthor) {
	return err;
	}
	foundAuthor.posts.push(newPost);
	newPost.author = foundAuthor;
	await newPost.save((error, savedPost) => {
	if (error) {
	return error;
	}
	return res.json(savedPost);
	});
	await foundAuthor.save((error, savedAuthor) => {
	if (error) {
	return error;
	}
	return res.json(savedAuthor);
	});
	return foundAuthor;
	});
	};

	exports.get = async function (req, res) {
	await PostModel.find({})
	.populate('author')
	.exec()
	.then((posts) => {
	res.json(posts);
	}, (err) => {
	res.send(err);
	});
	};

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How to query multiple mongo collections in express?

Hire the author: Odong Sunday

Why would one want to query multiple collections simultaneously?

Glossary

Project Setup Procedure

1. Primary Installations

2. Project dependencies

3. Setting up the models.

4. Setting up the controllers.

5. Setting up the views.

How can I create a Post (Article)?

A Post Request for a Post (Article)

Response on Postman

A Get Request for the list of posts

Populate and Exec method

Updating a post

We need to save the two objects now

Using Merge method in Lodash to update the post

Delete a Post

Querry the Author

Get a Post

Learning Tools.

Learning strategy

Reflective Analysis

Conclusion

Hire the author: Odong Sunday

Like this:

2 thoughts on “How to query multiple mongo collections in express?”

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	exports.update = function (req, res) {
	const newAuthorId = req.params.authorId;
	const { postId } = req.params;
	const newPost = req.body;

	PostModel.findOne({ _id: postId }, (err, post) => {
	if (!post) {
	return err;
	}

	const oldAuthorID = post.author._id;

	AuthorModel.findById(oldAuthorID)
	.then((oldAuthor) => {
	if (!oldAuthor) {
	return res.status(400).send('No Author with that Particular id');
	}

	const index = oldAuthor.posts.indexOf(postId);

	if (index > –1) {
	oldAuthor.posts.splice(index, 1);
	}

	oldAuthor.save((error, savedAuthor) => {
	if (error) {
	return error;
	}
	return savedAuthor;
	});
	return oldAuthor;
	});


	AuthorModel.findById(newAuthorId)
	.then((newAuthor) => {
	if (!newAuthor) {
	return err;
	}

	newAuthor.posts.push(post);
	newAuthor.save((error, savedAuthor) => {
	if (error) {
	return error;
	}
	return savedAuthor;
	});

	post.author = newAuthor;

	_.merge(post, newPost);
	post.save((error, saved) => {
	if (error) {
	return error;
	}
	return res.json(saved);
	});
	return newAuthor;
	});
	return post;
	});
	};

-exports.delete = async function (req, res) {
-  await PostModel.remove((req.post), (err, removed) => {
-    if (err) {
-      res.status(400).send('post not deleted');
-    } else {
-      res.json(removed);
-    }
-  });
-};

	exports.get = async function (req, res) {
	await AuthorModel.find({}).populate('posts')
	.exec()
	.then((authors) => {
	res.json(authors);
	}, (err) => {
	res.send(err);
	});
	};

	exports.params = async function (req, res, next, id) {
	console.log(id);
	await PostModel.findById(id)
	.populate('author')
	.exec()
	.then((post) => {
	if (!post) {
	return res.status(400).send(' post with that Particular id');
	}
	req.post = post;
	next();
	})
	.catch((err) => {
	res.send(err);
	});
	};

	exports.getOne = async function (req, res) {
	const post = await req.post;

	res.json(post);
	};

Hire the author: Odong Sunday

Why would one want to query multiple collections simultaneously?

Glossary

Project Setup Procedure

1. Primary Installations

2. Project dependencies

3. Setting up the models.

4. Setting up the controllers.

5. Setting up the views.

How can I create a Post (Article)?

A Post Request for a Post (Article)

Response on Postman

A Get Request for the list of posts

Populate and Exec method

Updating a post

We need to save the two objects now

Using Merge method in Lodash to update the post

Delete a Post

Querry the Author

Get a Post

Learning Tools.

Learning strategy

Reflective Analysis

Conclusion

Hire the author: Odong Sunday

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Like this:

2 thoughts on “How to query multiple mongo collections in express?”

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