Most Asked SQL Interview Questions -

Most Asked SQL Interview Questions with Answers

Are you looking for SQL Interview Questions? Are you preparing for SQL developer interview? This is the right place you have come. Here, we will guide and help you to enhance your SQL skills, and be prepare for job.

Here, we are providing a good collection of real-world Interview questions which are generally asked in big companies such as Google, Microsoft, Facebook, Oracle, and Amazon etc. Each question has a perfectly written answer. So, let’s start.

Que 1) What is SQL?/ Define SQL.

SQL is a short form of Structured Query Language. It is a domain-specific query language designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS) and used in programming.

It is mainly used to handle structured data that’s why it is called structured query language.

Que 2) What are the main advantages of SQL over older read–write APIs such as ISAM or VSAM?

SQL has the following main advantages over older read–write APIs such as ISAM or VSAM:

The biggest advantage of SQL is that it introduced the first concept of accessing many records with one single command.
In SQL, you don’t need to specify how to reach a record, e.g. with or without an index. It means, you can fetch a record easily by executing a query without specifying an index.

Que 3) On which technology SQL is based on?

SQL is based on the relational algebra and tuple relational calculus. The relational algebra is a theory that uses algebraic structures with a well founded semantics for modeling data, and defining queries on it. This is mainly used in database theory (SQL). This theory was introduced by Edgar F. Codd.

Tuple relational calculus or tuple calculus is a calculus that was created and introduced by Edgar F. Codd as a part of the relational model. It was introduced to provide a declarative database-query language for data manipulation in this data model. SQL Interview Questions

Que 4) Which paradigm does the SQL follow?

SQL follows the Declarative paradigm. The declarative paradigm or declarative programming is a programming paradigm which follows a style of building the structure and elements of computer programs that expresses the logic of a computation without the need of describing its control flow.

Some popular examples of declarative languages include database query languages such as SQL, XQuery, regular expressions, logic programming, functional programming, and configuration management systems.

Que) What types of statements does SQL consist of? / What are the subsets of SQL?

SQL consists of mainly 4 types of statements (also known as sublanguages):

Data Definition Language (DDL): It is mainly used to define the data structure. This category consists of the commands such as CREATE, ALTER, DROP, etc.

Data Control Language (DCL): It is mainly used to control the access to the data stored in the database. This category consists of the commands such as GRANT and REVOKE.

Data Manipulation Language (DML): It is mainly used to manipulate the existing data in the database. This category consists of the commands such as SELECT, UPDATE, INSERT, etc.

Transaction Control Language (TCL): It is mainly used to execute transaction operations in the database. This category consists of the commands such as COMMIT, ROLLBACK, SET TRANSACTION, SAVEPOINT, etc.

Que) Who is called the father of SQL?

SQL was initially designed and developed by Donald D. Chamberlin and Raymond F. Boyce at IBM. They were learning about the relational model from Edgar F. Codd in the early 1970s when they developed this. That version initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM’s original quasi-relational database management system, System R.

Que ) What is a Database?

A database is a collection of data stored in an organized manner. We can retrieve this organized data digitally from a remote or local computer system. In SQL database, the data is structured into tables, rows, columns, and indexes. So, the user can easily find the relevant information frequently. Due to its organized and structured behavior, an SQL database makes data access, data manipulation, data retrieval, data storing, and data management very easy. Every organization uses the database for storing the data. Databases can be huge and complex. Such databases are developed using fixed design and modeling approaches.

Following is the list of some common features of a database: