MongoDB is a cross-platform document-oriented and a non relational (i.e NoSQL) database program. It is an open-source document database, that stores the data in the form of key-value pairs.
What is a MongoDB Query?
MongoDB query is used to specify the selection filter using query operators while retrieving the data from the collection by db.find() method. We can easily filter the documents using the query object. To apply the filter on the collection, we can pass the query specifying the condition for the required documents as a parameter to this method, which is an optional parameter for db.find() method.
Query Selectors: Following is the list of some operators used in the queries in MongoDB.
| Operation | Syntax | Description |
|---|---|---|
| Equality | {“key” : “value”} | Matches values that are equal to a specified value. |
| Less Than | {“key” :{$lt:”value”}} | Matches values that are less than a specified value. |
| Greater Than | {“key” :{$gt:”value”}} | Matches values that are greater than a specified value. |
| Less Than Equal to | {“key” :{$lte:”value”}} | Matches values that are less than or equal to a specified value. |
| Greater Than Equal to | {“key” :{$gte:”value”}} | Matches values that are greater than or equal to a specified value. |
| Not Equal to | {“key”:{$ne: “value”}} | Matches all values that are not equal to a specified value. |
| Logical AND | { “$and”:[{exp1}, {exp2}, …, {expN}] } | Joins query clauses with a logical AND returns all documents that match the conditions of both clauses. |
| Logical OR | { “$or”:[{exp1}, {<exp2}, …, {expN}] } | Joins query clauses with a logical OR returns all documents that match the conditions of either clause. |
| Logical NOT | { “$not”:[{exp1}, {exp2}, …, {expN}] } | Inverts the effect of a query expression and returns documents that do not match the query expression. |
The Database or Collection on which we operate:
Example 1:
Python3
# importing Mongoclient from pymongofrom pymongo import MongoClient# Making Connectionmyclient = MongoClient("mongodb://localhost:27017/") # databasedb = myclient["mydatabase"] # Created or Switched to collection# names: GeeksForGeeksCollection = db["GeeksForGeeks"]# Filtering the Quantities greater# than 40 using query.cursor = Collection.find({"Quantity":{"$gt":40}})# Printing the filtered data.print("The data having Quantity greater than 40 is:")for record in cursor: print(record) # Filtering the Quantities less# than 40 using query.cursor = Collection.find({"Quantity":{"$lt":40}})# Printing the filtered data.print("\nThe data having Quantity less than 40 is:")for record in cursor: print(record) |
Output:
Example 2:
Python3
# importing Mongoclient from pymongofrom pymongo import MongoClient# Making Connectionmyclient = MongoClient("mongodb://localhost:27017/") # databasedb = myclient["mydatabase"] # Created or Switched to collection# names: GeeksForGeeksCollection = db["GeeksForGeeks"]# Filtering the (Quantities greater than# 40 AND greater than 40) using AND query.cursor = Collection.find({"$and":[{"Quantity":{"$gt":40}}, {"Quantity":{"$gt":50}}]})# Printing the filtered data.print("Quantities greater than 40 AND\Quantities greater than 40 :")for record in cursor: print(record)# Filtering the (Quantities greater than# 40 OR greater than 40) using OR query.cursor = Collection.find({"$or":[{"Quantity":{"$gt":40}}, {"Quantity":{"$gt":50}}]})# Printing the filtered data.print()print("Quantities greater than 40 OR\Quantities greater than 40 :")for record in cursor: print(record) |
Output:
