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December 24, 2011 MySql, MySQL 0 Comments 3,005 views

MySQL Interview Questions – Part 1

1) What’s MySQL ?
MySQL (pronounced “my ess cue el”) is an open source relational database management system (RDBMS) that uses Structured Query Language (SQL), the most popular language for adding, accessing, and processing data in a database. Because it is open source, anyone can download MySQL and tailor it to their needs in accordance with the general public license. MySQL is noted mainly for its speed, reliability, and flexibility. …

2) What is DDL, DML and DCL ?
If you look at the large variety of SQL commands, they can be divided into three large subgroups. Data Definition Language deals with database schemas and descriptions of how the data should reside in the database, therefore language statements like CREATE TABLE or ALTER TABLE belong to DDL. DML deals with data manipulation, and therefore includes most common SQL statements such SELECT, INSERT, etc. Data Control Language includes commands such as GRANT, and mostly concerns with rights, permissions and other controls of the database system.

3) How do you get the number of rows affected by query?
SELECT COUNT (user_id) FROM users would only return the number of user_id’s.

4) If the value in the column is repeatable, how do you find out the unique values?
Use DISTINCT in the query, such as SELECT DISTINCT user_firstname FROM users; You can also ask for a number of distinct values by saying SELECT COUNT (DISTINCT user_firstname) FROM users;

5) How do you return the a hundred books starting from 25th?
SELECT book_title FROM books LIMIT 25, 100. The first number in LIMIT is the offset, the second is the number.