Manual:category table

The category table tracks all existing categories. Something is a category if it has an entry somewhere in categorylinks table

Categories might not have corresponding pages, so they need to be tracked separately. cat_pages, cat_subcats, and cat_files are signed to make underflow more obvious.

Primary key

Name of the category, in the same form as page .page_title (with underscores). If there is a category page corresponding to this category, by definition, it has this name (in the Category namespace).

Number of pages in the category. This number includes the number of subcategories and the number of files.

Number of sub-categories in the category.

Number of files (i.e. Image: namespace members) in the category.

Was reserved for future use; apparently no one found a use for it because it was removed in v1.20. Instead, the status of hidden categories is stored in the page_props table as the property "hiddencat" in pp_propname.

DESCRIBEcategory;

+-------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+------------------+------+-----+---------+----------------+
| cat_id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| cat_title | varbinary(255) | NO | UNI | NULL | |
| cat_pages | int(11) | NO | MUL | 0 | |
| cat_subcats | int(11) | NO | | 0 | |
| cat_files | int(11) | NO | | 0 | |
+-------------+------------------+------+-----+---------+----------------+

DESCRIBEcategory;

+-------------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+---------------------+------+-----+---------+----------------+
| cat_id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| cat_title | varbinary(255) | NO | UNI | NULL | |
| cat_pages | int(11) | NO | MUL | 0 | |
| cat_subcats | int(11) | NO | | 0 | |
| cat_files | int(11) | NO | | 0 | |
| cat_hidden | tinyint(3) unsigned | NO | | 0 | |
+-------------+---------------------+------+-----+---------+----------------+

SHOWINDEXINcategory;

+----------+------------+-----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+----------+------------+-----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| category | 0 | PRIMARY | 1 | cat_id | A | 0 | NULL | NULL | | BTREE | | |
| category | 0 | cat_title | 1 | cat_title | A | 0 | NULL | NULL | | BTREE | | |
| category | 1 | cat_pages | 1 | cat_pages | A | 0 | NULL | NULL | | BTREE | | |
+----------+------------+-----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

• MediaWiki database tables