Manual:Templatelinks table

Contains for each current page inclusion the id of the host page, the namespace number of the included page, and its title without namespace.

The target page may or may not exist, and due to renames and deletions may refer to different page records as time goes by.

tl_from
Key to the page_id of the page containing the link.

tl_namespace
Key to page_namespace of the target page. Used in conjunction with tl_title.

tl_title
Key to page_title of the target page. Used in conjunction with tl_namespace.

Schema summary
DESCRIBE templatelinks; on MediaWiki 1.16 gives the following: +--+--+--+-+-+---+ +--+--+--+-+-+---+ +--+--+--+-+-+---+
 * Field       | Type             | Null | Key | Default | Extra |
 * tl_from     | int(10) unsigned | NO   | PRI | 0       |       |
 * tl_namespace | int(11)         | NO   | PRI | 0       |       |
 * tl_title    | varbinary(255)   | NO   | PRI |         |       |

DESCRIBE templatelinks; on MediaWiki 1.9 gives the following: +--+-+--+-+-+---+ +--+-+--+-+-+---+ +--+-+--+-+-+---+
 * Field       | Type            | Null | Key | Default | Extra |
 * tl_from     | int(8) unsigned | NO   | PRI | 0       |       |
 * tl_namespace | int(11)        | NO   | PRI | 0       |       |
 * tl_title    | varchar(255)    | NO   | PRI | NULL    |       |

DESCRIBE templatelinks; on MediaWiki 1.8 gives the following: +--+-+--+-+-+---+ +--+-+--+-+-+---+ +--+-+--+-+-+---+
 * Field       | Type            | Null | Key | Default | Extra |
 * tl_from     | int(8) unsigned | NO   | PRI | 0       |       |
 * tl_namespace | int(11)        | NO   | PRI | 0       |       |
 * tl_title    | varchar(255)    | NO   | PRI | NULL    |       |

This table is new in version 1.6.

DESCRIBE templatelinks; on MediaWiki 1.6 gives the following: +---+-+--+-+---+---+ +---+-+--+-+---+---+ +---+-+--+-+---+---+
 * Field        | Type                | Null | Key | Default   | Extra |
 * tl_from      | int(8)              | NO   | PRI | 0         |       |
 * tl_namespace | tinyint(2) unsigned | NO   | PRI |           |       |
 * tl_title     | varchar(255)        | NO   | PRI | 0         |       |