Skip to main content

MongoDB Questions and answers

Is MongoDB NoSQL database and which kind of NoSQL supported by MongoDB?
Yes MongoDB is based on NoSQL store model. MongoDB is document oriented database in which data objects are store as separate documents inside a collection and does not follow RDBMS.The documents are stored as binary JSON or BSON object.
click here for MongoDB overview

What is namespace in MongoDB?
Concatenation of collection name with database name is called namespace. for example db.book where db is database name and book is the collection name.

What is advantage of MongoDB over SQL database?
MongoDB is document oriented database which is allow highly flexible and scalable feature. MongoDb is schema less means no fixed structure database like SQL. One collection is flexible regarding fields means one row have 10 field, second can have12 fields. MongoDB database is more faster to SQL database due to efficient indexing and storage techniques. Advantage of MongoDB

What is projection in MongoDB
If we want to select necessary field's data then we have to use projection. For more click here

Syntax to create database and collection
syntax to create database
>use database_name
syntax to create collection
>db.createcollection("collection name")
To read More 

Does MongoDB is support foreign key
No, MongoDB does not support foreign key.

What is sharding in MongoDB
Sharding is responsible to storing data records across multiple machines. As per demand to manage large amount of data, a single machine is not sufficient to store data nor provide an acceptable medium to read and write data. To resolve this problem MongoDB provide a process called Sharding. Sharding solve the problem with horizontal scaling. Through sahrding, you may add more machines to support data growth and demands of read and write operations. know more

what is a replica set in MongoDB  
A replica set is a group of MongoDB instances that host the same data set. There is two node first is primary node that receives all write operations and secondary, apply operations from the primary so that they have the same data set. Replica set can have only one primary node. know more

Can you move old files in the moveChunk directory?
Yes, it is possible to move old files in the moveChunk directory, during normal shard balancing operations these files are made as backups and can be deleted once the operations are done.

What is indexing in MongoDB
As we know index is technique to arrange data in database which support the efficient resolution of queries. If we run a query to select data, MongoDB do scan every document of collection. Scanning of all document may affect performance of MongoDB when it process the large volume of data.
The index stores the value of a specific field or set of fields, ordered by the value of the field as specified in index. know more
 

Popular posts from this blog

Remove special character from string in MongoDB

Problem: Suppose wehave a collection and one field is type string contains some special character (like !@#$%) and we don’t want these special character.
Solution: We can easily remove the special character from field using script “replace(/[^a-zA-Z 0-9 ]/g, '')” in our query.  How can we remove special character from string using this script please see following example.
Example: Suppose we have a collection “EduSurvey “where we are collecting information from institutions.

{Name:"JB institute”, About:"This is good one collage for MBA", Information:"This $%%institute ##has good faculty etc$$"}
{Name:"MK institute”, About:"This is good one collage for MCA", Information:"This$$%# is the dummy text12"}
{Name:"MG institute”, About:"This is good one collage for B,Tech", Information:"This# institute@ has&* good infrastructure"}

Did you notice Information fields contains some special character so we…

What is difference between UNION and UNION ALL in SQL Server

We use UNION and UNION ALL operator to combine multiple results set into one result set.
UNION operator is used to combining multiple results set into one result set but removes any duplicate rows. Basically, UNION is used to performing a DISTINCT operation across all columns in the result set. UNION operator has the extra overhead of removing duplicate rows and sorting result.
UNION ALL operator use to combine multiple results set into one result set but it does not remove any duplicate result. Actually, this does not remove duplicate rows so it is faster than the UNION operator. If you want to combine multiple results and without duplicate records then use UNION otherwise UNION ALL is better.
Following some rules for using UNION/UNION ALL operator
1.The number of the column should be the same in the query's when you want to combine them. 2.The column should be of the same data type. 3.ORDER BY clause can be applied to the overall result set not within each result set.
4.Column name of …

Installing PostgreSQL on Windows

Installing PostgreSQL on Windows Follow the following step to install PostgreSQL on windows. Step 1: Download the expected version suitable for you from the link https://www.enterprisedb.com/downloads/postgres-postgresql-downloads#windows Step 2: Double click on the installer file, an installation wizard will appear and guide you through multiple steps where you can choose different options that you would like to have in PostgreSQL. The following illustrates each step and its options for installation. If you install a different version, you may get additional steps. Step 3: In this step of the installation process would be to select the directories for installation location where PostgreSQL would be installed. By default, it is stored under the C:\\ProgramFile. Step 4: Enter the password for the database super-user and service account. Step 5: Enter the port for PostgreSQL. Make sure that no other applications are using this port. Leave it as default if you are unsure. Step 6: Choose the de…