Thecategory table tracks all existing categories.Something is a category if it has an entry somewhere incategorylinks table

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

Primary key

Name of the category, in the same form aspage.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 thepage_props table as the property "hiddencat" inpp_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      |         |               |+----------+------------+-----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

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