Let us create a collection with documents −> db.demo178.insertOne({"DueDate":new ISODate("2019-01-10T06:18:20.474Z")}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e397bd89e4f06af551997f5") } > db.demo178.insertOne({"DueDate":new ISODate("2020-11-10T18:05:11.474Z")}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e397bf39e4f06af551997f6") } > db.demo178.insertOne({"DueDate":new ISODate("2020-03-15T07:05:10.474Z")}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e397c039e4f06af551997f7") } > db.demo178.insertOne({"DueDate":new ISODate("2020-06-11T16:05:10.474Z")}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e397c0f9e4f06af551997f8") }Display all documents from a collection with the help of find() method −> db.demo178.find();This will produce the following output −{ "_id" : ObjectId("5e397bd89e4f06af551997f5"), "DueDate" : ISODate("2019-01-10T06:18:20.474Z") } { "_id" : ObjectId("5e397bf39e4f06af551997f6"), "DueDate" : ISODate("2020-11-10T18:05:11.474Z") } { "_id" : ObjectId("5e397c039e4f06af551997f7"), "DueDate" : ISODate("2020-03-15T07:05:10.474Z") ... Read More

To add a document in an already created collection, use $push in MongoDB. Let us create a collection with documents −> db.demo177.insertOne(    { "Id": "101", "details": [         { "StudentName": "Chris",  "Scores": [67, 71, 74], "SubjectName": ["MySQL", "Java"]  },       { "StudentName": "David", "Scores": [89, 98, 45], "SubjectName": ["PL/SQL", "C"] } ]    } ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e384b2b9e4f06af551997f4") }Display all documents from a collection with the help of find() method −> db.demo177.find().pretty();This will produce the following output −{    "_id" : ObjectId("5e384b2b9e4f06af551997f4"),    "Id" : "101",    "details" ... Read More

To get substring, use $substr in MongoDB. Let us create a collection with documents −> db.demo176.insertOne({"ProductName":"PRODUCT-1"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3843a09e4f06af551997ef") } > db.demo176.insertOne({"ProductName":"PRODUCT-102"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3843a69e4f06af551997f0") } > db.demo176.insertOne({"ProductName":"PRODUCT-105"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3843aa9e4f06af551997f1") }Display all documents from a collection with the help of find() method −> db.demo176.find();This will produce the following output −{ "_id" : ObjectId("5e3843a09e4f06af551997ef"), "ProductName" : "PRODUCT-1" } { "_id" : ObjectId("5e3843a69e4f06af551997f0"), "ProductName" : "PRODUCT-102" } { "_id" : ObjectId("5e3843aa9e4f06af551997f1"), "ProductName" : "PRODUCT-105" }Following is the query to get substring in MongoDB ... Read More

To count only collections that match two fields, use count(). Let us create a collection with documents −> db.demo175.insertOne({"EmployeeName":"Bob", "isMarried":"YES"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3840969e4f06af551997e8") } > db.demo175.insertOne({"EmployeeName":"David", "isMarried":"NO"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e38409e9e4f06af551997e9") } > db.demo175.insertOne({"EmployeeName":"Mike", "isMarried":"YES"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3840a79e4f06af551997ea") } > db.demo175.insertOne({"EmployeeName":"Sam", "isMarried":"NO"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3840ae9e4f06af551997eb") }Display all documents from a collection with the help of find() method −> db.demo175.find();This will produce the following output −{ "_id" : ObjectId("5e3840969e4f06af551997e8"), "EmployeeName" : "Bob", "isMarried" : "YES" } { "_id" ... Read More

To evaluate one or more values, use $or along with find(). Let us create a collection with documents −> db.demo174.insertOne({"StudentName":"Chris", "CountryName":"US"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e383c709e4f06af551997e5") } > db.demo174.insertOne({"StudentName":"David", "CountryName":"UK"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e383c779e4f06af551997e6") } > db.demo174.insertOne({"StudentName":"Bob", "CountryName":"AUS"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e383c7e9e4f06af551997e7") }Display all documents from a collection with the help of find() method −> db.demo174.find();This will produce the following output −{ "_id" : ObjectId("5e383c709e4f06af551997e5"), "StudentName" : "Chris", "CountryName" : "US" } { "_id" : ObjectId("5e383c779e4f06af551997e6"), "StudentName" : "David", "CountryName" : "UK" } { "_id" : ... Read More

To limit the number of values in a field, use MongoDB $slice. Let us create a collection with documents −> db.demo173.insertOne({"ListOfValues":[10, 40, 100, 560, 700, 900]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e383a4f9e4f06af551997e4") }Display all documents from a collection with the help of find() method −> db.demo173.find().pretty();This will produce the following output −{    "_id" : ObjectId("5e383a4f9e4f06af551997e4"),    "ListOfValues" : [10, 40, 100, 560, 700, 900 ] }Following is the query to limit number of values in a field using MongoDB −> db.demo173.find({}, { "ListOfValues": { "$slice": -2 } } );This will produce the following output −{ "_id" ... Read More

To find a value in lowercase, use the toLowerCase() method in MongoDB. Use the method in find() to find the value in lowercase.Let us create a collection with documents −> db.demo172.insertOne({"SubjectName":"MySQL"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3838ce9e4f06af551997e1") } > db.demo172.insertOne({"SubjectName":"mongodb"}); {     "acknowledged" : true,    "insertedId" : ObjectId("5e3838d69e4f06af551997e2") } > db.demo172.insertOne({"SubjectName":"MongoDB"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3838db9e4f06af551997e3") }Display all documents from a collection with the help of find() method −> db.demo172.find();This will produce the following output −{ "_id" : ObjectId("5e3838ce9e4f06af551997e1"), "SubjectName" : "MySQL" } { "_id" : ObjectId("5e3838d69e4f06af551997e2"), "SubjectName" : "mongodb" } ... Read More

To re-map the fields of a MongoDB collection, use update() along with $rename. Let us first create a collection with documents −> db.demo171.insertOne( { "Name": "Chris", "Details": { "SubjectName": "MySQL", "CountryName": "US" } } ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3837 399e4f06af551997e0") }Display all documents from a collection with the help of find() method −> db.demo171.find();This will produce the following output −{ "_id" : ObjectId("5e3837399e4f06af551997e0"), "Name" : "Chris", "Details" : { "SubjectName" : "MySQL", "CountryName" : "US" } }Following is the query to re-map the fields of a MongoDB collection −> db.demo171.update({}, { $rename : { 'Name' ... Read More

Problem statementMean is the average of the given data set calculated by dividing the total sum by the number of values in the data set.Mode of a data set is the value that appears most frequently in a series of dataIf our dataset is {1, 2, 3, 4} then mean value is − (1 + 2 + 3 + 4) / 4 = 2.5If our dataset is {1, 2, 3, 4, 1, 1, 1, 1} then mode value is − 1 as it appears 5 times.ExampleFirst, create a table −CREATE TABLE NUMBERS (    value INT )Insert data into the ... Read More

Mysql is one of the most widely used open source Dbs. Python provides ways to connect to this DB and use the DB to store and retrive the data from it.Install pymysqlDepending on the python environment you are using, pymysql package can be installed using one of the following methods.# From python console pip install pymysql #Using Anaconda conda install -c anaconda pymysql # Add modules using any python IDE pymysqlConnecting to MySqlNow we can connect to the Mysql environment using the following code. After connecting we are finding out the version of the DB.Exampleimport pymysql # Open database connection ... Read More