Manual:User newtalk table

The user_newtalk table stores the IDs or IP addresses of users whose talk pages have been changed. This information is used for the display of the "you have new messages" box. The respective row is deleted when the user looks at the page.

user_id
Key to  or "0" for anonymous users.

user_ip
If the user is an anonymous user their IP address is stored here since the user_id of 0 is ambiguous.

user_last_timestamp
Timestamp for getting the difference since last view.

Schema summary
+-+--+--+-+-+---+ +-+--+--+-+-+---+ +-+--+--+-+-+---+
 * Field              | Type             | Null | Key | Default | Extra |
 * user_id            | int(10) unsigned | NO   | MUL | 0       |       |
 * user_ip            | varbinary(40)    | NO   | MUL |         |       |
 * user_last_timestamp | varbinary(14)   | YES  |     | NULL    |       |

+-+---+--+-+-+---+ +-+---+--+-+-+---+ +-+---+--+-+-+---+
 * Field              | Type          | Null | Key | Default | Extra |
 * user_id            | int(11)       | NO   | MUL | 0       |       |
 * user_ip            | varbinary(40) | NO   | MUL | NULL    |       |
 * user_last_timestamp | varbinary(14) | YES |     | NULL    |       |

+-+---+--+-+-+---+ +-+---+--+-+-+---+ +-+---+--+-+-+---+
 * Field              | Type          | Null | Key | Default | Extra |
 * user_id            | int(11)       | NO   | MUL | 0       |       |
 * user_ip            | varbinary(40) | NO   | MUL | NULL    |       |
 * user_last_timestamp | binary(14)   | NO   |     | NULL    |       |

+-+---+--+-+-+---+ +-+---+--+-+-+---+ +-+---+--+-+-+---+
 * Field  | Type          | Null | Key | Default | Extra |
 * user_id | int(11)      | NO   | MUL | 0       |       |
 * user_ip | varbinary(40) | NO  | MUL | NULL    |       |

+-+-+--+-+-+---+ +-+-+--+-+-+---+ +-+-+--+-+-+---+
 * Field  | Type        | Null | Key | Default | Extra |
 * user_id | int(5)     | NO   | MUL | 0       |       |
 * user_ip | varchar(40) | NO  | MUL | NULL    |       |