Upgrade Database ################

.. contents:: :local: :depth: 2

Documentations

• Database Reference Documentation CodeIgniter 3.x <http://codeigniter.com/userguide3/database/index.html>_
• :doc:Working with Databases Documentation CodeIgniter 4.x </database/index>

What has been changed

• The functionality in CI3 is basically the same as in CI4.
• Database Caching <https://www.codeigniter.com/userguide3/database/caching.html>_ functionality known from CI3 was removed.
• The method names have changed to camelCase and the :doc:Query Builder <../database/query_builder> now needs to be initialized before you can run queries on it.

Upgrade Guide

1. Add your database credentials to app/Config/Database.php. The options are pretty much the same as in CI3 only some names have changed slightly.

2. Everywhere you have used the database you have to replace $this->load->database(); with $db = db_connect();.

3. If you use multiple databases use the following code to load additional databases $db = db_connect('group_name');.

4. Now you have to change all database queries. The most important change here is to replace $this->db with just $db and adjust the method name and $db. Here are some examples:

   • $this->db->query('YOUR QUERY HERE'); to $db->query('YOUR QUERY HERE');
   • $this->db->simple_query('YOUR QUERY') to $db->simpleQuery('YOUR QUERY')
   • $this->db->escape("something") to $db->escape("something");
   • $this->db->affected_rows(); to $db->affectedRows();
   • $query->result(); to $query->getResult();
   • $query->result_array(); to $query->getResultArray();
   • echo $this->db->count_all('my_table'); to echo $db->table('my_table')->countAll();

5. To use the new Query Builder Class you have to initialize the builder $builder = $db->table('mytable'); after that you can run the queries on the $builder. Here are some examples:

   • $this->db->get() to $builder->get();
   • $this->db->get_where('mytable', array('id' => $id), $limit, $offset); to $builder->getWhere(['id' => $id], $limit, $offset);
   • $this->db->select('title, content, date'); to $builder->select('title, content, date');
   • $this->db->select_max('age'); to $builder->selectMax('age');
   • $this->db->join('comments', 'comments.id = blogs.id'); to $builder->join('comments', 'comments.id = blogs.id');
   • $this->db->having('user_id', 45); to $builder->having('user_id', 45);

6. CI4 does not provide Database Caching <https://www.codeigniter.com/userguide3/database/caching.html>_ layer known from CI3, so if you need to cache the result, use :doc:../libraries/caching instead.

7. If you use limit(0) in Query Builder, CI4 returns all records in stead of no records due to a bug. But since v4.5.0, you can change the incorrect behavior with a setting. So change the setting. See :ref:v450-query-builder-limit-0-behavior for details.

Code Example

CodeIgniter Version 3.x

.. literalinclude:: upgrade_database/ci3sample/001.php

CodeIgniter Version 4.x

.. literalinclude:: upgrade_database/001.php