SQL, or Structured Query Language, is the standard language used to define, query, and manipulate data stored in a relational database. It provides a declarative way to describe what data you want rather than how to retrieve it step by step.
Key Points: • SQL is declarative -- you specify what result you want, and the database engine's query optimizer figures out how to execute it efficiently. • It covers four areas: defining structure (DDL), manipulating data (DML), controlling access (DCL), and managing transactions (TCL). • SQL is standardized by ANSI/ISO, though every database (MySQL, PostgreSQL, Oracle, SQL Server) adds its own extensions and dialect quirks. • It is used across virtually every application that stores structured, relational data.
Example: A simple SQL statement like SELECT name FROM employees WHERE department = 'Engineering' tells the database what data to return without specifying the underlying algorithm used to scan or index the table.
Code Example:
SELECT name FROM employees WHERE department = 'Engineering';Interview Tip: A concise interview answer is:
"SQL, or Structured Query Language, is the standard declarative language for defining, querying, and manipulating data in a relational database. I describe the result I want with statements like SELECT, INSERT, or UPDATE, and the database engine decides the most efficient way to execute it."