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MySQL Interview Questions

MySQL Interview Questions

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Table of Contents

• MySQL Queries
• MySQL Basics
• RDBMS Questions

Q. What are indexes in a Database? What are the types of indexes

An index is a database structure that you can use to improve the performance of database activity. A database table can have one or more indexes associated with it. An index is defined by a field expression that you specify when you create the index. Typically, the field expression is a single field name, like EMP_ID.

Q. What are the different tables present in MySQL

Note that MySQL supports two different kinds of tables: transaction-safe tables (InnoDB and BDB) and non-transaction-safe tables (HEAP, ISAM, MERGE, and MyISAM). Advantages of transaction-safe tables (TST): Safer.

Q. What are the technical features of MySQL

Relational Database Management System (RDBMS) MySQL is a relational database management system.

1. Easy to use. MySQL is easy to use.
2. It is secure.
3. Client/ Server Architecture.
4. Free to download.
5. It is scalable.
6. Speed.
7. High Flexibility.

Q. Explain SELECT, LIKE, IN, Regular-Expression, Datatypes, Sub-Query in mySQL

Q. Explain JOIN Query in mySQL

A JOIN clause is used to combine rows from two or more tables, based on a related column between them.
Take users table and orders table for example.
Users

user_id	name	mobile
1	John	123
2	Joe	124

Orders

order_id	user_id	total	created_at
1	1	500	2021-12-19 18:32:00
2	1	800	2021-12-03 08:32:00
3	2	50	2021-12-13 12:49:00
4	1	80	2021-12-15 21:19:00

So to get the list of orders with names and mobile nos. for each order, we can join orders and users on the basis of user_id.

select o.*, u.name, u.mobile from ordes o join users u on o.user_id = u.user_id;

Q. Explain Stored Procedure, View, Event, triggers in mySQL

Q. Explain Transaction in mySQL

Q. What is difference between procedures and triggers

Q. How do you find third highest salary

select * from employees order by salary limit 2,1;

Q. How to prevent from database attacks/SQL Injection

Q. How many TRIGGERS are possible in MySql

Q. What are Heap tables

Q. What is the difference between BLOB AND TEXT

Q. Explain advantages of MyISAM over InnoDB

Q. What are the differences between MySQL_fetch_array(), MySQL_fetch_object(), MySQL_fetch_row()

Q. How to find the unique values if the value in the column is repeated

Q. Define REGEXP

Q. Difference between CHAR and VARCHAR

Both of them are used for string type data. char has fixed length and if the inserted data is less than the defined length, required no. of blank spaces are added as padding. varchar has variable length and no padding is used to fill up the left out space. So technically, varchar will save space.

Q. Give string types available for column

Q. What are the nonstandard string types

Q. What are all the Common SQL Function