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

Primary KeyPrimary Key is a column that is used to uniquely identify each tuple of the table.It is used to add integrity constraints to the table. Only one primary key is allowed to be used in a table. Duplicate and NULL (empty) values are not valid in the case of the primary key. Primary keys can be used as foreign keys for other tables too.Let’s take an example, We have a table name employee which stores data of employees of a company. The below table shows the contents of the table.Emp_idNamePh_No.PositionSalaryEmp_id here is primary key of the table. As the ... Read More

When it comes to two of the most talked about technologies in present times, Big Data and Internet of Things (IoT) are perhaps right at the helm. And over the last few years, Big Data has made progress in numerous domains. And although Internet of Things happens to be different, it is massively linked to Big Data.What is Big Data?Big Data is essentially a large amount of data that is in complex form. Specifically, it also refers to the use of predictive analysis and methods that allows extraction of valuable information from such data. This allows better decision making, reduction ... Read More

Data Lake and Data Warehouse both are used for storing big data. A Data Lake is a very big storage repository which is used to store raw unstructured data, machine to machine, logs flowing through in real-time. The purpose of the stored data is not defined in a data lake. They are stored for future analysis of the data. A data warehouse is a repository for structured, filtered data that has already been processed for a specific purpose. A Data warehouse collects the data from multiple sources and transforms the data using ETL process, then loads it to the Data ... Read More

Big Data is everywhere and there is an urgent need to collect and preserve whatever data has been generated. We also find that there is a greater fear of missing something, which is important. Big Data Analytics has become crucial, it helps improve business, decision making and offers the biggest edge over the competitors.What does the term Big Data mean?The term big data can be described as something large volume of data which is both structured and unstructured, that inundates a business on a day-to-day basis. Data is available everywhere but how can organizations capitalize on that is the big ... Read More

Technology is pervading into all aspects of real estate, making its functioning easier and quicker. And with the rising need to manage client demands, converting leads into sales, along with the requirement for broad property research, it is becoming all the more imperative to make use of multifaceted technologies that aid in causing consequential changes in the real estate business.Over the last few years, along with the emergence of new technologies, the existing ones have also witnessed a turnaround with added features to support the increasing requirements. These include a larger usage of precast construction, building information modeling process offering ... Read More

Big Data is basically a term that covers large and complex data sets. To handle it, one requires use of different data processing applications when compared with traditional types.While there are various applications that allow handling and processing of big data, the base framework has always been that of Apache Hadoop.What is Apache Hadoop?Hadoop is an open-source software framework written in Java and comprises of two parts, which are the storage part and the other being the data processing part. The storage part is called the Hadoop Distributed File System (HDFS) and the processing part is called MapReduce.We now look ... Read More