160 Must‑Know MySQL Interview Questions to Test Your Skills

SQL (Structured Query Language) is a database query language used for accessing, querying, updating, and managing relational database systems.

MySQL is a relational database management system developed by MySQL AB and now owned by Oracle; it is one of the most popular RDBMSs for web applications and Java enterprise development because it is open‑source and free.

Differences among MySQL, Oracle, and Sql Service:

Sql Service runs only on Windows, while MySQL and Oracle are cross‑platform.

MySQL is free and open‑source; Sql Service and Oracle require payment.

In terms of size, MySQL is the smallest, Sql Service medium, Oracle the largest.

Oracle supports high concurrency and large traffic; MySQL may need clustering or caching for heavy load.

Oracle provides fine‑grained user permissions; MySQL grants full access once a login is allowed.

Installation footprint: MySQL occupies a few hundred megabytes, whereas Oracle requires several gigabytes and consumes more memory.

The three normal forms:

First Normal Form: each column holds atomic values.

Second Normal Form: non‑key columns depend fully on the whole primary key.

Third Normal Form: non‑key columns depend only on the primary key, not on other non‑key columns.

When designing databases, follow the normal forms unless performance considerations justify denormalization.

MySQL permission tables stored in the mysql database include user, db, table_priv, columns_priv, and host, each controlling access at different granularity levels.