SQL Interview Questions

1.What is SQL?

SQL or Sequel is Structured Query Language which is used for fetching and storing data in a relational database and performing various manipulation on these stored data such as creation, deletion, insertion etc.

2. What is Relational Database?

Relational Database or Relational Database Management System (RDBMS) stores data in tables with some defined relationship in the tables . The tables will have rows and columns.

3. What are examples of Relational Databases?

  • Oracle
  • Microsoft SQL Server
  • Postgre SQL
  • MySQL
  • SQLite
  • HyperSQL

4. What is a Non- Relational Database?

A Non Relational Database, also called NoSQL (NotOnlySQL) database does not store data in the table format in schemas with rows and column. It may store data as JSON documents, key/value pairs, graphs. With no concepts of schemas here, there is scope of storing all kinds of documents.

5. What are different types of Non – Relational Database?

  • Document Database
  • Key/Value Database
  • Graph Database
  • Column-Family Database
  • Time Series Database
  • Object Database
  • External Index Database

6. What are examples of Non-Relational Databases?

  • MongoDB
  • Redis
  • Apache Cassandra
  • Couchbase
  • Apache HBase

7. What are the benefits or advantages of using Relational Database?

  • Data Integrity – Parent child relationship concept ensures data integrity
  • Normalization – It ensures no variance in data in the database.
  • High Security – Database table access can be limited to specific users
  • Ease of use – complex queries can be fired easily
  • Collaboration – Multiple users can access the same database at same time.
  • Simplicity– A simple SQL query is good enough for fetching data for most of the users
  • Network Access– Users can access database via a database client thru a network

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