PHP-MYSQL |  mysqli_fetch_assoc() VS  mysqli_fetch_array()

mysqli_fetch_assoc() function fetch a result row as an associative array where as mysqli_fetch_array() function fetch a result row as an associative array, a numeric array, or both.

PHP-MYSQL |  mysqli_fetch_object () VS  mysqli_fetch_array()

mysqli_fetch_object()  fetch a result row as an object where as mysqli_fetch_array()  fetch a result row as an associative array, a numeric array, or both.

PHP-MYSQL |  Fetch Recoards From MySql table

There are 4 ways:

1. mysqli_fetch_row() - Get a result row as an enumerated array
2. mysqli_fetch_array() - Fetch a result row as an associative array, a numeric array, or both
3. mysqli_fetch_object() - Fetch a result row as an object
4. mysqli_fetch_assoc() - Fetch a result row as an associative array

OPTIMIZE command is use for optimize a table.

 OPTIMIZE TABLE `users` 

For increaseing the speed of a query we have to do couple of things

• First of all instead of using select * from table1, use select column1, column2, column3.. from table1.
• Try to introduce index in the table.
• Always use limit keyword if we are looking for any specific number of rows from the result set.

DATEDIFF function is use for finding the number of days between two given dates using MySQL

 DATEDIFF(‘2018-03-07′,’2017-01-01’)

Bellow code is use for the same

 $sql = "SELECT * FROM table1";
$result = mysql_query($sql, $db_link);
$num_rows = mysql_num_rows($result);
echo $num_rows;

The three different way in PHP to connect with MySQL is:

1. MySQL
2. MySQLI
3. PDO

Note: We should use MySQLI because MySQLI is imporoved version of MySQL and have more function then MySQL.

Mostly we use:

• utf8_general_ci
• utf8_unicode_ci

utf8_general_ci is use for fast sorting but it is less accurate whereas utf8_unicode_ci is used for better accuracy but little slow as compare to utf8_general_ci.

We can also use other collation based on specific languages like utf8_swedish_ci.

There are 5 different types of storage engine present in MySql.

1. MyISAM
2. Heap
3. Merge
4. INNO DB
5. ISAM

MyISAM is the default storage engine for MySQL

Cross-site scripting (XSS)

Cross-site scripting (XSS) is a type of computer security vulnerability typically found in web applications. XSS enables attackers to inject client-side script into web pages viewed by other users. A cross-site scripting vulnerability may be used by attackers to bypass access controls such as the same-origin policy.

By using mysql function mysqli_insert_id() we can retrive the last inserted id in database table.