A: SQL, or Structured Query Language, is a standardized programming language used for managing and manipulating relational databases. It is essential for performing tasks such as querying data, updating records, and managing database structures.
SQL Interview Questions
Total Questions: 8
1. What is SQL
Level: Basic
2. What is Relational Database Management System (RDBMS)
Level: Basic
A: A Relational Database Management System (RDBMS) is a type of database management system that stores data in a structured format using rows and columns, allowing efficient data operations while maintaining relationships between data entities.
3. What is a Database?
Level: Basic
A: A database is an organized collection of structured information or data, typically stored electronically in a computer system. Databases are managed by Database Management Systems (DBMS), which allow users to create, read, update, and delete data efficiently. They are essential for applications that require data storage, retrieval, and management.
4. What is primary key?
Level: Basic
A: A primary key is a unique identifier for a record in a database table. It ensures that each record can be uniquely distinguished from others, preventing duplicate entries. A primary key can consist of one or more columns and must contain unique values, which are essential for maintaining data integrity and establishing relationships between tables in a relational database.
5. What is foreign key?
Level: Basic
A: A foreign key is a field (or collection of fields) in one table that uniquely identifies a row of another table. It establishes a relationship between the two tables, ensuring referential integrity by enforcing that the value in the foreign key column(s) must match a value in the primary key column(s) of the referenced table. This relationship allows for the linking of data across different tables in a relational database.
6. What is unique key?
Level: Basic
A: A unique key is a constraint that ensures all values in a column (or a set of columns) are distinct from one another, meaning no two rows can have the same value in that column(s). Unlike a primary key, a unique key can accept null values, but each non-null value must be unique. This constraint helps maintain data integrity by preventing duplicate entries in a database table.
7. What is table?
Level: Basic
A: A table is a collection of related data entries that consists of rows and columns. Each table represents a specific entity, and each row in the table corresponds to a unique record, while each column represents a specific attribute of that entity. Tables are fundamental components of a relational database, allowing for the organization and management of data in a structured format. Relationships between tables can be established through keys, enabling efficient data retrieval and integrity.
8. What is field?
Level: Basic
A: A field is a single piece of data or attribute within a record in a database table. Each field represents a specific characteristic of the entity that the table describes. Fields are organized into columns, and each record in the table consists of multiple fields, allowing for the structured storage and retrieval of data. Fields are essential for defining the properties of the data stored in a relational database.