-> This is the world’s second most popular and widely used open source database.

-> All the database names, table names and table fields name are case sensitive.

-> To switch from one database to another database

cmd:USE database_name;  

-> To list all the databases

cmd: show databases;

-> To see the tables

cmd: show tables;

-> To select the first record

cmd:SELECT column_name  FROM table_name LIMIT 1;  

Mysql_connect:

Every time you need to open and close database connection, depending on the request.

Mysql_pconnect:

It opens a persistent connection to the database that can not be closed.

 i_am_a_dummy flag:

It enables MySQL engine to refuse any UPDATE or DELETE statement to execute if the WHERE clause is not present.

To find Nth highest salary is:

 cmd:select distinct(salary) from employee order by salary desc limit n-1,1  

Default Port of Mysql:
The default port of MySQL Server is 3306.

To retrieve a hundred books starting from 20th:

SELECT book_title FROM books LIMIT 20, 100;

DataDirectory:
The default location of MySQL data directory in windows is C:\mysql\data or C:\Program Files\MySQL\MySQL Server 5.0 \data.