Manual:Redirect table

Contains for each page that is currently a redirect (i.e., not for old revisions which are redirects) the id of the source page, the target namespace number, and the target page title without namespace.

The target page may or may not exist.

''NOTE: as of August 2007, database dumps for Wikipedia and other Wikimedia projects as provided on http://download.wikimedia.org/ have incomplete data in this table: only redirect pages that have been created or edited recently are present. For older redirects, resort to using the pagelinks table.''

DESCRIBE mw_redirect; in version 1.9 gives the following: mysql> describe mw_redirect; +--+-+--+-+-+---+ +--+-+--+-+-+---+ +--+-+--+-+-+---+ 3 rows in set (0.02 sec)
 * Field       | Type            | Null | Key | Default | Extra |
 * rd_from     | int(8) unsigned | NO   | PRI | 0       |       |
 * rd_namespace | int(11)        | NO   | MUL | 0       |       |
 * rd_title    | varchar(255)    | NO   |     | NULL    |       |