Nov 11 min read

Important MongoDB Crud Operations | Realcode4you

Software requirement

The following software is used in today’s workshop:

MongoDB 6.0

• Installation instructions:

Studio 3T

• https://studio3t.com/

Here is an online tool that includes MongoDB and MapReduce, it has a 30 day trial but if you need more time you can also apply for a student license

CRUD operations

1. $nin

db.inventory.find({quantity:{$nin:[5, 15]}})

Selects all documents from the inventory collection where the quantity does not equal either 5 or 15

db.inventory.find({quantity:{$not:{$in:[5, 15]}}})

2. $exists

db.inventory.find({qty:{$exists:true}})

This query will select all documents in the inventory collection where the qty field exists.

3. $gt

db.inventory.find({quantity:{$gt:20}})

Select all documents in the inventory collection where quantity is greater than 20.

4. $lt

db.inventory.find({quantity:{$lt:20}})

Select all documents in the inventory collection where quantity is less than 20.

MongoDB can compare numbers in string format and it is done based on string comparison rules.

It compares Unicode code points of characters.

Ex.,:

5. Finding textual patterns (Contain)

db.inventory.find({context:{$regex:"Sydney"}})

db.inventory.find({context:{$regex:/Sydney/}})

db.inventory.find({context:/Sydney/})

Select all documents in the inventory collection where context contains “Sydney” word.

6. Finding textual patterns (Start with)

db.inventory.find({context:{$regex:"^Sydney"}})

db.inventory.find({context:{$regex:/^Sydney/}})

db.inventory.find({context:/^Sydney/})

Select all documents in the inventory collection where context starts with “Sydney” word.

7. Finding textual patterns (End with)

db.inventory.find({context:{$regex:"Sydney$"}})

db.inventory.find({context:{$regex:/Sydney$/}})

db.inventory.find({context:/Sydney$/})

Select all documents in the inventory collection where context ends with “Sydney” word

Display operations

1. Display contents of specific fields.

db.Tweets.find({query statement},{"display field1":1, "display field2":1})

2. Sort results according to values of a field.

db.Tweets.find({query statement}).sort({"sort field":1})

3. Count results.

db.Tweets.find({query statement}).count()

4. Return limited number of results.

db.Tweets.find({query statement}).limit(number)

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