How to set a primary key in MongoDB

Question

I want to set one of my fields as primary key  I am using MongoDB as my NoSQL

User · Answer

Simple you can use db collectionName createIndex  urfield 1   unique true

User · Answer

This is the syntax of creating primary key      db  lt  collection   createIndex   lt  key and index type specification       unique  true       Let s take that our database have collection named student and it s document have key named student id which we need to make a primary key  Then the command should be like below   db student createIndex  student id 1   unique true     You can check whether this student id set as primary key by trying to add duplicate value to the student collection   prefer this document for further informations  https   docs mongodb com manual core index-unique  create-a-unique-index

User · Answer

If you re using Mongo on Meteor  you can use  ensureIndex   CollectionName  ensureIndex  field 1     unique  true

User · Answer

id field is reserved for primary key in mongodb  and that should be a unique value  If you don t set anything to  id it will automatically fill it with  MongoDB Id Object   But you can put any unique info into that field   Additional info  http   www mongodb org display DOCS BSON  Hope it helps

User · Answer

The other way is to create Indexes for your collection and  make sure that they are unique   You can find more on the following link  I actually find this pretty simple and easy to implement

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If you thinking like RDBMS  you can t create primary key  Default primary key is  id  But you can create Unique Index  Example is bellow  db members createIndex     quot user id quot   1      unique  true      db members insert   user id  1  name   nanhe     db members insert   name   kumar     db members find     Output is bellow     quot  id quot    ObjectId  quot 577f9cecd71d71fa1fb6f43a quot     quot user id quot    1   quot name quot     quot nanhe quot       quot  id quot    ObjectId  quot 577f9d02d71d71fa1fb6f43b quot     quot name quot     quot kumar quot    When you try to insert same user id mongodb throws a write error  db members insert   user id  1  name   aarush     WriteResult    quot nInserted quot    0   quot writeError quot       quot code quot    11000   quot errmsg quot     quot E11000 duplicate key error collection  student members index  user id 1 dup key      1 0   quot

User · Answer

One way of achieving this behaviour is by setting the value to  id  which is reserved for a primary key in MongoDB  field based on the custom fields you want to treat as primary key  i e  If I want employee id as the primary key then at the time of creating document in MongoDB  assign  id value same as that of employee id

User · Answer

http   docs mongodb org manual tutorial create-an-auto-incrementing-field   You can also check this link and auto-increment the  id field

User · Answer

In mongodb  id field is reserved for primary key  Mongodb use an internal ObjectId value if you don t define it in your object and also create an index to ensure performance   But you can put your own unique value for  id and Mongodb will use it instead of making one for you  And even if you want to use multiple field as primary key you can use an object      id     a   1  b  1      Just be careful when creating these ids that the order of keys  a and b in the example  matters  if you swap them around  it is considered a different object

[mongodb] How to set a primary key in MongoDB?

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