| #################### |
| Database Forge Class |
| #################### |
| |
| The Database Forge Class contains functions that help you manage your |
| database. |
| |
| .. contents:: Table of Contents |
| |
| **************************** |
| Initializing the Forge Class |
| **************************** |
| |
| .. important:: In order to initialize the Forge class, your database |
| driver must already be running, since the forge class relies on it. |
| |
| Load the Forge Class as follows:: |
| |
| $this->load->dbforge() |
| |
| Once initialized you will access the functions using the $this->dbforge |
| object:: |
| |
| $this->dbforge->some_function() |
| |
| $this->dbforge->create_database('db_name') |
| ============================================ |
| |
| Permits you to create the database specified in the first parameter. |
| Returns TRUE/FALSE based on success or failure:: |
| |
| if ($this->dbforge->create_database('my_db')) { echo 'Database created!'; } |
| |
| $this->dbforge->drop_database('db_name') |
| ========================================== |
| |
| Permits you to drop the database specified in the first parameter. |
| Returns TRUE/FALSE based on success or failure:: |
| |
| if ($this->dbforge->drop_database('my_db')) { echo 'Database deleted!'; } |
| |
| **************************** |
| Creating and Dropping Tables |
| **************************** |
| |
| There are several things you may wish to do when creating tables. Add |
| fields, add keys to the table, alter columns. CodeIgniter provides a |
| mechanism for this. |
| |
| Adding fields |
| ============= |
| |
| Fields are created via an associative array. Within the array you must |
| include a 'type' key that relates to the datatype of the field. For |
| example, INT, VARCHAR, TEXT, etc. Many datatypes (for example VARCHAR) |
| also require a 'constraint' key. |
| |
| :: |
| |
| $fields = array( 'users' => array( 'type' => 'VARCHAR', 'constraint' => '100', ), ); // will translate to "users VARCHAR(100)" when the field is added. |
| |
| |
| Additionally, the following key/values can be used: |
| |
| - unsigned/true : to generate "UNSIGNED" in the field definition. |
| - default/value : to generate a default value in the field definition. |
| - null/true : to generate "NULL" in the field definition. Without this, |
| the field will default to "NOT NULL". |
| - auto_increment/true : generates an auto_increment flag on the |
| field. Note that the field type must be a type that supports this, |
| such as integer. |
| |
| :: |
| |
| $fields = array( 'blog_id' => array( 'type' => 'INT', 'constraint' => 5, 'unsigned' => TRUE, 'auto_increment' => TRUE ), 'blog_title' => array( 'type' => 'VARCHAR', 'constraint' => '100', ), 'blog_author' => array( 'type' =>'VARCHAR', 'constraint' => '100', 'default' => 'King of Town', ), 'blog_description' => array( 'type' => 'TEXT', 'null' => TRUE, ), ); |
| |
| |
| After the fields have been defined, they can be added using |
| $this->dbforge->add_field($fields); followed by a call to the |
| create_table() function. |
| |
| $this->dbforge->add_field() |
| ---------------------------- |
| |
| The add fields function will accept the above array. |
| |
| Passing strings as fields |
| ------------------------- |
| |
| If you know exactly how you want a field to be created, you can pass the |
| string into the field definitions with add_field() |
| |
| :: |
| |
| $this->dbforge->add_field("label varchar(100) NOT NULL DEFAULT 'default label'"); |
| |
| |
| Note: Multiple calls to add_field() are cumulative. |
| |
| Creating an id field |
| -------------------- |
| |
| There is a special exception for creating id fields. A field with type |
| id will automatically be assinged as an INT(9) auto_incrementing |
| Primary Key. |
| |
| :: |
| |
| $this->dbforge->add_field('id'); // gives id INT(9) NOT NULL AUTO_INCREMENT |
| |
| |
| Adding Keys |
| =========== |
| |
| Generally speaking, you'll want your table to have Keys. This is |
| accomplished with $this->dbforge->add_key('field'). An optional second |
| parameter set to TRUE will make it a primary key. Note that add_key() |
| must be followed by a call to create_table(). |
| |
| Multiple column non-primary keys must be sent as an array. Sample output |
| below is for MySQL. |
| |
| :: |
| |
| $this->dbforge->add_key('blog_id', TRUE); // gives PRIMARY KEY `blog_id` (`blog_id`) $this->dbforge->add_key('blog_id', TRUE); $this->dbforge->add_key('site_id', TRUE); // gives PRIMARY KEY `blog_id_site_id` (`blog_id`, `site_id`) $this->dbforge->add_key('blog_name'); // gives KEY `blog_name` (`blog_name`) $this->dbforge->add_key(array('blog_name', 'blog_label')); // gives KEY `blog_name_blog_label` (`blog_name`, `blog_label`) |
| |
| |
| Creating a table |
| ================ |
| |
| After fields and keys have been declared, you can create a new table |
| with |
| |
| :: |
| |
| $this->dbforge->create_table('table_name'); // gives CREATE TABLE table_name |
| |
| |
| An optional second parameter set to TRUE adds an "IF NOT EXISTS" clause |
| into the definition |
| |
| :: |
| |
| $this->dbforge->create_table('table_name', TRUE); // gives CREATE TABLE IF NOT EXISTS table_name |
| |
| |
| Dropping a table |
| ================ |
| |
| Executes a DROP TABLE sql |
| |
| :: |
| |
| $this->dbforge->drop_table('table_name'); // gives DROP TABLE IF EXISTS table_name |
| |
| |
| Renaming a table |
| ================ |
| |
| Executes a TABLE rename |
| |
| :: |
| |
| $this->dbforge->rename_table('old_table_name', 'new_table_name'); // gives ALTER TABLE old_table_name RENAME TO new_table_name |
| |
| |
| **************** |
| Modifying Tables |
| **************** |
| |
| $this->dbforge->add_column() |
| ============================= |
| |
| The add_column() function is used to modify an existing table. It |
| accepts the same field array as above, and can be used for an unlimited |
| number of additional fields. |
| |
| :: |
| |
| $fields = array( 'preferences' => array('type' => 'TEXT') ); $this->dbforge->add_column('table_name', $fields); // gives ALTER TABLE table_name ADD preferences TEXT |
| |
| An optional third parameter can be used to specify which existing column |
| to add the new column after. |
| |
| :: |
| |
| $this->dbforge->add_column('table_name', $fields, 'after_field'); |
| |
| |
| $this->dbforge->drop_column() |
| ============================== |
| |
| Used to remove a column from a table. |
| |
| :: |
| |
| $this->dbforge->drop_column('table_name', 'column_to_drop'); |
| |
| |
| $this->dbforge->modify_column() |
| ================================ |
| |
| The usage of this function is identical to add_column(), except it |
| alters an existing column rather than adding a new one. In order to |
| change the name you can add a "name" key into the field defining array. |
| |
| :: |
| |
| $fields = array( 'old_name' => array( 'name' => 'new_name', 'type' => 'TEXT', ), ); $this->dbforge->modify_column('table_name', $fields); // gives ALTER TABLE table_name CHANGE old_name new_name TEXT |
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