How to List foreign keys in Mysql

By | November 14, 2023

information_schema The following query will list out the foreign keys in mysql. It finds it out from the information_schema database. select concat(table_name, '.', column_name) as 'foreign key', concat(referenced_table_name, '.', referenced_column_name) as 'references' from information_schema.key_column_usage where referenced_table_name is not null; The output is a clean table listing out all foreign keys from all databases +———————–+————-+ |… Read More »

Create foreign key using Phpmyadmin

By | May 9, 2020

The innodb storage engine supports foreign keys in Mysql. To create foreign keys in phpmyadmin : 1. Convert both tables into innodb, if they are not already. 2. View the structure of the table which will have a foreign key. Make the referencing field an INDEX. 3. Now come back to structure view and click… Read More »

Create AutoIncrement column/field in Apache Derby

By | July 6, 2009

While creating a table a particular column / field can be made autoincrement as : CREATE TABLE students ( id INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1), name VARCHAR(24) NOT NULL, address VARCHAR(1024), CONSTRAINT primary_key PRIMARY KEY (id) ) ; The value of an autoincrement column increments automatically with… Read More »

PHP redirect – go back to previous page

By | September 1, 2023

To go back to the previous page the superglobal variable $_SERVER can be used. $_SERVER[‘HTTP_REFERER’] has the link to the previous page. So to redirect simply : // Method to go to previous page function goback() { header("Location: {$_SERVER['HTTP_REFERER']}"); exit; } goback();

Backup mysql database with php and zip it

By | May 1, 2009

Many php applications prefer to backup the mysql database from within the application and save it as an archive. The mysqldump commandline utility can be used to perform this function of backing up a mysql database as sql file. The command would be like this : mysqldump –user=$username –password=$password –opt $db_name > $dir/backup.sql The above… Read More »

Php – parse text and convert urls into hyperlinks

By | May 10, 2020

The following function will parse a given text and convert all the urls into links. It does this using regular expressions. It converts email addresses to mailto links as well. Code function parse_links($str) { $str = str_replace('www.', 'http://www.', $str); $str = preg_replace('|http://([a-zA-Z0-9-./]+)|', '<a href="http://$1">$1</a>', $str); $str = preg_replace('/(([a-z0-9+_-]+)(.[a-z0-9+_-]+)*@([a-z0-9-]+.)+[a-z]{2,6})/', '<a href="mailto:$1">$1</a>', $str); return $str; }