SQL Interview Question and Answers(Database)

The following are the most popular and useful SQL interview questions and answers for fresher and experienced candidates. These questions are created specifically to familiarise you with the types of questions you might encounter during your SQL interview

Q) What Is a Database?

A database is a collection of organized data, information and records. It contains information about one enterprise. It maintains any information that may be necessary to the decision-making process involved in the management of that organization.

Q) Advantages of DBMS?

The advantages provided by a DBMS are:

·        Reduce redundancy

·        Controlled data inconsistency

·        Shared data

·        Standardized data

·        Secure data

·        Integrated data

Q) Purpose of Database?

The database is information that a person needs in his personal, business, and social life. The power and purpose of the information are not only in collecting and finding them but more importantly in using them. In a typical file system, it becomes very tedious to read, write, search, manipulate or update records.

Q) Kind of Database?

Structured Database

• Data in form of records or files of information arranged in a uniform format.
• These databases are usually storage of information with similar entries such as a list of persons born in a country, a medical database of patients data, an inventory database of a company and many others.

Free-Form/Unstructured Database

• It is a loose collection of information, such as those you will find on the world wide web.
• A collection of your documents on the computer made from several programs can be considered a free-form database.

Q) Types of Databases?

Operational Database

• It is a dynamic database that is used by any organization in its day-to-day operation.
• They are used to collect data, maintain, modify and delete data.
• Also known as transactional Database

Analytical Database

• It is a static database, where data is rarely modified. This Database is often used to store and track historical data to make long-term projections and analyses.
• More referenced in Big Data Domain.

Q) What IS RDBMS?

• RDBMS stands for Relational Database Management System.
• RDBMS is the basis for SQL and SQL, and for all modern database systems such as MS SQL Server, IBM DB2, Oracle, MYSQL, and Microsoft Access.
• The Data in RDBMS is stored in database objects called tables. A table is a collection of related data entries and consists of columns and rows.

Q) Things you can do with RDBMS?

·        Create a database

·        Information storage

·        Information retrieval

·        Information management

·        Information analysis

        Print and share information

Q) What is Data?

It is a number or value found and stored in the database. Data is static because it remains the same it is modified by a process.

Q) What is Information?         

It is data that has been processed thereby making it relevant and meaningful to the person viewing it. Information is dynamic because it changes relative to the data stored in the database and it could be processed in many ways.

Q) What is NULL handling in the Database?

It is used to represent a value that is unknown or missing. A null value is neither a zero nor a blank.

Q) What is a table in the Database?

It is the main structure in the relational database. It is composed of attributes (fields) and domain (records). A table almost always represents a subject that can be an object (person, place or thing) or an event.

Q) How to find a degree of Table?

The degree of the Table is the number of columns in the Table.

Q) What are Records?

It refers to a specific person, place, thing or event. Record is also known as the “tuple” in relational database terminology. It pertains to structure in the database table representing a unique instance of a subject.

Q) What are Views in the Database?

It is also known as a virtual table. It is called a virtual table since it does not hold data on its own; rather it gets data from the table on which it is based. And since it comes from other tables it is composed of several fields coming from one or more data.

Q What is a Relationship?

They exist when two or more tables have a connection or association.

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