Manual:Redirect table

The 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 and the information about target. The target page may or may not exist.

Fields
A target is broken into four parts: interwiki prefix (should be empty for a regular redirect), namespace, title and fragment.

rd_from
Contains the of the source page.

rd_namespace
Contains the number of the target's.

rd_title
Contains the sanitized title of the target page. It is stored as text, with spaces replaced by underscores.

rd_fragment
Contains the target's fragment ID if present (see also 218 ), otherwise is NULL.

rd_interwiki
This field is not empty only if an is used: #REDIRECT &#91;[prefix:…]] (a prefix such as " w: " for Wikipedia, or an interlanguage link prefix such as "nl:" for Dutch, but not both). In this case a redirect is not visible in Special:WhatLinksHere (even if the target lies in the same wiki), is always 0 and  may contain a possible namespace prefix, but  may be non-NULL.

Schema summary
+--+--+--+-+-+---+ +--+--+--+-+-+---+ +--+--+--+-+-+---+
 * Field       | Type             | Null | Key | Default | Extra |
 * rd_from     | int(10) unsigned | NO   | PRI | 0       |       |
 * rd_namespace | int(11)         | NO   | MUL | 0       |       |
 * rd_title    | varbinary(255)   | NO   |     |         |       |
 * rd_interwiki | varbinary(32)   | YES  |     | NULL    |       |
 * rd_fragment | varbinary(255)   | YES  |     | NULL    |       |

+--+-+--+-+-+---+ +--+-+--+-+-+---+ +--+-+--+-+-+---+
 * Field       | Type                | Null | Key | Default | Extra |
 * rd_from     | int(10) unsigned    | NO   | PRI | 0       |       |
 * rd_namespace | int(11)            | NO   | MUL | 0       |       |
 * rd_title    | varchar(255) binary | NO   |     | NULL    |       |

+--+-+--+-+-+---+ +--+-+--+-+-+---+ +--+-+--+-+-+---+
 * 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) binary | NO   |     | NULL    |       |

Indexes
 +--++-+--+--+---+-+--++--++-+---+ +--++-+--+--+---+-+--++--++-+---+ +--++-+--+--+---+-+--++--++-+---+
 * Table   | Non_unique | Key_name    | Seq_in_index | Column_name  | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
 * redirect |         0 | PRIMARY     |            1 | rd_from      | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
 * redirect |         1 | rd_ns_title |            1 | rd_namespace | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
 * redirect |         1 | rd_ns_title |            2 | rd_title     | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
 * redirect |         1 | rd_ns_title |            3 | rd_from      | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |