Table of Contents
Can I use joins in MongoDB?
MongoDB does not allow joins, but you can use plugins to handle that.
How do Joins work in MongoDB?
MongoDB is not a relational database, but you can perform a left outer join by using the $lookup stage. The $lookup stage lets you specify which collection you want to join with the current collection, and which fields that should match.
What is the maximum size of a MongoDB document?
16 megabytes
The maximum BSON document size is 16 megabytes. The maximum document size helps ensure that a single document cannot use excessive amount of RAM or, during transmission, excessive amount of bandwidth. To store documents larger than the maximum size, MongoDB provides the GridFS API.
Is join inefficient?
No. Despite the protests of NoSQL proponents, joins are not inherently slow in Relational database systems. Joining two or more tables will certainly take more resources and runtime than just querying one of the involved tables, after all there will be more data to plod through.
Why are joins bad?
The problem is joins are relatively slow, especially over very large data sets, and if they are slow your website is slow. It takes a long time to get all those separate bits of information off disk and put them all together again.
What is the difference between join and join in MongoDB?
In SQL databases, a user can execute a JOIN operation between two tables inside identical or different databases. While the case in MongoDB for JOIN is varied, MongoDB lets JOIN operations perform between two collections implemented in a similar database.
What is the use of $lookup in MongoDB?
This stage $lookup allows you to state which collection a user needs to join with the present collection and also which fields that must match. In MongoDB it is quite difficult to relate data from one collection to another excluding when basic script query functions are used.
How many fields can be added to a MongoDB document?
We can add as many fields as necessary, but all MongoDB documents require an _id field which has a unique value. The _id is similar to an SQL primary key, and will be inserted automatically if necessary. Our social network now requires a post collection, which stores numerous insightful updates from users.
Are MongoDB collections relational?
Relational purists may be feeling uneasy already, as if we were violating some universal law. But let’s bear in mind that MongoDB collections are not equivalent to relational tables; each serves a unique design objective.