SQL Interview Question

1.What is Database?

A database is an organized collection of data, stored and retrieved digitally from a remote or local computer system. Databases can be vast and complex, and such databases are developed using fixed design and modeling approaches.

2.What is SQL?

SQL stands for the Structured Query Language. It is the standard language used to maintain the relational database and perform many different data manipulation operations on the data. SQL was initially invented in 1970. It is a database language used for database creation, deletion, fetching and modifying rows, etc. sometimes, it is pronounced as 'sequel.' We can also use it to handle organized data comprised of entities (variables) and relations between different entities of the data.

3.What is DBMS?

DBMS stands for Database Management System. DBMS is a system software responsible for the creation, retrieval, updation, and management of the database. It ensures that our data is consistent, organized, and is easily accessible by serving as an interface between the database and its end-users or application software.

4. What are the usages of SQL?

SQL is responsible for maintaining the relational data and the data structures present in the database. Some of the common usages are given below:

• To execute queries against a database
• To retrieve data from a database
• To inserts records in a database
• To updates records in a database
• To delete records from a database
• To create new databases
• To create new tables in a database
• To create views in a database
• To perform complex operations on the database.

 

 5. What are the subsets of SQL?

The following are the four significant subsets of the SQL:

• Data definition language (DDL): It defines the data structure that consists of commands like CREATE, ALTER, DROP, etc.
• Data manipulation language (DML): It is used to manipulate existing data in the database. The commands in this category are SELECT, UPDATE, INSERT, etc.
• Data control language (DCL): It controls access to the data stored in the database. The commands in this category include GRANT and REVOKE.
• Transaction Control Language (TCL): It is used to deal with the transaction operations in the database. The commands in this category are COMMIT, ROLLBACK, SET TRANSACTION, SAVEPOINT, etc.

6. What are Tables and Fields?

A table is an organized collection of data stored in the form of rows and columns. Columns can be categorized as vertical and rows as horizontal. The columns in a table are called fields while the rows can be referred to as records