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punbb13:database_helpers 2010/04/09 07:33 punbb13:database_helpers 2020/02/06 11:04 current
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-====== Database helpers ======+====== PunBB 1.3 database helpers ======
PunBB has an implementation of the database layer class. It takes into account the forum configuration and works with different databases. PunBB has an implementation of the database layer class. It takes into account the forum configuration and works with different databases.
On ''include/common.php'' inclusion an instance of this database layer named ''$forum_db'' is being created in global scope to provide database helpers. On ''include/common.php'' inclusion an instance of this database layer named ''$forum_db'' is being created in global scope to provide database helpers.
-==== Performing a query ====+Please remember the following when use PunBB database layer: 
 +  * Potentially harmful data is escaped using ''$forum_db->escape()''. Expected integer values should be forced into integer form using ''intval()'' before being used in a query. 
 +  * Use the SQL 2003 style [[http://en.wikipedia.org/wiki/Join_(SQL)#Inner_join|explicit join notation]]. 
 +  * Database helper functions have an optional parameter ''$no_prefix''. The prefix of table names is being selected during the forum installation and is available in the database layer class (''$forum_db->prefix''). The database layer is able to add the prefix to table names automatically (the default behavior). It's recommended not to change the default value of ''$no_prefix''. 
 + 
 +===== Performing a query =====
  * **Direct query** (not recommended). You can simply write an SQL-statement and execute it.   * **Direct query** (not recommended). You can simply write an SQL-statement and execute it.
-<code php> $result = $forum_db->query('SELECT * FROM topics WHERE id = 10');</code>+<code php> $result = $forum_db->query('SELECT * FROM '.$forum_db->prefix.'topics WHERE id = 10');</code>
Be sure, that your SQL code is cross-compatible with all database engines supported by PunBB. Be sure, that your SQL code is cross-compatible with all database engines supported by PunBB.
-  * **Using [[query builder]]** (recommended). You may transparently build database queries. All the specific of database engines and database structure will automatically be taken in account. Example of usage:+  * **Using query builder** (recommended). You may transparently build database queries. All the specific of database engines and database structure will automatically be taken in account. Example of usage:
<code php>$query = array( <code php>$query = array(
  'SELECT'  => '*',   'SELECT'  => '*',
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$result = $forum_db->query_build($query); $result = $forum_db->query_build($query);
</code> </code>
-See [[query builder]] page for details. 
-===== Data Manipulation with query builder ======+Let's discuss how to use the query builder.
-First consider the DML (Data Manipulation Language) part of the PunBB database layer class.+===== Query Builder: Data Manipulation ======
==== SELECT ==== ==== SELECT ====
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$forum_db->query_build($query) or error(__FILE__, __LINE__);</code> $forum_db->query_build($query) or error(__FILE__, __LINE__);</code>
-===== Data Definition with query builder ======+===== Data Definition ======
Now let's consider the DDL (Data Definition Language) part of the PunBB database layer class. Now let's consider the DDL (Data Definition Language) part of the PunBB database layer class.
-==== Creating a table ====+==== Tables ====
-The query structure is actually an array which accepts following parameters: +<code php>function table_exists($table_name, $no_prefix = false)</code> 
-  * **FIELDS:** Fields is an array, with the keys being field names and the values being an array of data about the field. The field data contains a key datatype that should be mapped to one of the acceptable field types, a key allow_null which should be set to either true or false, and an optional key default which specifies a default value for the field. + 
-  * **PRIMARY KEY:** An array whose elements are field names from FIELDS. +This function returns ''true'' if the table with ''$table_name'' name exists and ''false'' otherwise. 
-  * **UNIQUE KEYS:** An array with keys that act as the name of unique indexes and values that are arrays of field names (again, the field names should match field names in FIELDS). + 
-  * **INDEXES:** An array with keys that act as the name of indexes and values that are arrays of field names (again, the field names should match field names in FIELDS). +<code php>function create_table($table_name, $schema, $no_prefix = false)</code> 
-  * **ENGINE:** This element is optional and is __only used by MySQL__. It specifies the database engine that MySQL should use in creating this table.+ 
 +Takes either two or three parameters and creates a database table. The first parameter is the name of the table to be added. The second is an array of schema for the table itself (see the explanation and example below). The third is the optional parameter ''$no_prefix''. 
 + 
 +<code php>function drop_table($table_name, $no_prefix = false)</code> 
 + 
 +Deletes the table that has the ''$table_name'' name. 
 + 
 +=== Creating a table === 
 + 
 +==Table structure== 
 +The table structure is described by an array which accepts following parameters: 
 +  * ''FIELDS:'' Fields is an array, with the keys being field names and the values being an array of data about the field. The field data contains a key datatype that should be mapped to one of the acceptable field types, a key allow_null which should be set to either true or false, and an optional key default which specifies a default value for the field. 
 +  * ''PRIMARY KEY:'' An array whose elements are field names from ''FIELDS''. 
 +  * ''UNIQUE KEYS:'' An array with keys that act as the name of unique indexes and values that are arrays of field names (again, the field names should match field names in FIELDS). 
 +  * ''INDEXES:'' An array with keys that act as the name of indexes and values that are arrays of field names (again, the field names should match field names in ''FIELDS''). 
 +  * ''ENGINE:'' This element is optional and //is only used by MySQL//. It specifies the database engine that MySQL should use in creating this table.
==Acceptable field types== ==Acceptable field types==
-When adding a column or creating a new table, you must specify the data type for each field. The following data-types are acceptable to use in the helper functions (create_table and add_field). These data-types are guaranteed to be translated properly when used. +When adding a column or creating a new table, you must specify the data type for each field. The following data-types are acceptable to use in the helper functions (''create_table()'' and ''add_field()''). These data-types are guaranteed to be translated properly when used. 
-  * **SERIAL** (translates to INT(10) UNSIGNED AUTO_INCREMENT in MySQL) +  * ''SERIAL'' (translates to ''INT(10) UNSIGNED AUTO_INCREMENT'' in MySQL) 
-  * **TINYINT/SMALLINT/MEDIUMINT/INT/BIGINT (##) UNSIGNED** (UNSIGNED and (##) are optional) +  * ''TINYINT/SMALLINT/MEDIUMINT/INT/BIGINT (##) UNSIGNED'' (''UNSIGNED'' and ''(##)'' are optional) 
-  * **VARCHAR/CHAR** +  * ''VARCHAR/CHAR'' 
-  * **TINYTEXT/MEDIUMTEXT/TEXT/LONGTEXT** +  * ''TINYTEXT/MEDIUMTEXT/TEXT/LONGTEXT'' 
-  * **FLOAT** +  * ''FLOAT'' 
-  * **DOUBLE**+  * ''DOUBLE''
-__To developers__: Don't use __$query__ in extensions as this variable is used in the core and might interfere with it. Rather use a specific variable for your script to avoid errors.+**Note**: Don't use ''$query'' in extension code that has global scope as this variable is used in the core and might interfere with it. Rather use a specific variable for your script to avoid errors.
<PHP> <PHP>
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</PHP> </PHP>
-After creating the query, a method of the database class is used:+After creating the schema, a method of the database class is used:
<PHP>$forum_db->create_table('categories', $schema);</PHP> <PHP>$forum_db->create_table('categories', $schema);</PHP>
-The create_table function takes either two or three parameters. The first parameter is the name of the table to be added. The second is an array of schema for the table itself. The third parameter, which is optional, specifies whether or not to add the database prefix to the table name. If the third parameter is not specified or is set to false, the prefix will be prepended to the table name. If it is specified as true, the prefix will not be prepended. +==== Fields ==== 
 + 
 +<code php>function field_exists($table_name, $field_name, $no_prefix = false)</code> 
 + 
 +Checks if the field ''$field_name'' is present in the table ''$table_name''. 
 + 
 +<code php>function add_field($table_name, $field_name, $field_type, $allow_null, $default_value = null, $after_field = null, $no_prefix = false)</code> 
 + 
 +Adds a field to the ''$table_name'' table. One can specify the name of an existent field, ''$after_field'', to insert after it the field to be added. The meaning of the other parameters is clear from its names. 
 + 
 +<code php>function alter_field($table_name, $field_name, $field_type, $allow_null, $default_value = null, $after_field = null, $no_prefix = false)</code> 
 + 
 +Modifies the ''$field_name'' field. The meaning of parameters is the same as above. 
 + 
 +<code php>function drop_field($table_name, $field_name, $no_prefix = false)</code> 
 + 
 +Removes the ''$field_name'' field from the ''$table_name'' table. 
 + 
 +Here are examples of the fields manipulation. 
 + 
 +<code php>// Taken from admin/db_update.php 
 +$forum_db->alter_field('posts', 'poster_ip', 'VARCHAR(39)', true); 
 +$forum_db->alter_field('users', 'registration_ip', 'VARCHAR(39)', false, '0.0.0.0');</code> 
 + 
 +<code php>// Taken from the pun_pm extension 
 +// Install section 
 +if (!$forum_db->field_exists('users', 'pun_pm_new_messages')) 
 +  $forum_db->add_field('users', 'pun_pm_new_messages', 'INT(10)', true); 
 + 
 +// Uninstall section 
 +$forum_db->drop_field('users', 'pun_pm_new_messages');</code> 
 + 
 +==== Indexes ==== 
 + 
 +<code php>function index_exists($table_name, $index_name, $no_prefix = false)</code> 
 + 
 +Checks if the index ''$index_name'' is present in the table ''$table_name''. 
 + 
 +<code php>function add_index($table_name, $index_name, $index_fields, $unique = false, $no_prefix = false)</code> 
 + 
 +Adds an index to the ''$table_name'' table. ''$index_fields'' is the array of fields to be added to the index. 
 + 
 +<code php>function drop_index($table_name, $index_name, $no_prefix = false)</code> 
 + 
 +Removes the ''$index_name'' index from the ''$table_name'' table. 
 + 
 +Here are examples of the indexes manipulation. 
 + 
 +<code php>// Taken from admin/db_update.php 
 +if (!$forum_db->index_exists('online', 'user_id_ident_idx')) 
 +{ 
 +  ... 
 +  $forum_db->add_index('online', 'user_id_ident_idx', array('user_id', 'ident'), true); 
 +  ... 
 +} 
 + 
 +$forum_db->drop_index('online', 'user_id_idx');</code>

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