Manual:Ipblocks table

The ipblocks table stores details of IP addresses and users who have been blocked from editing.

DESCRIBE ipblocks; gives the following:

+--+--+--+-+++ +--+--+--+-+++ +--+--+--+-+++
 * Field               | Type             | Null | Key | Default        | Extra          |
 * ipb_id              | int(11)          | NO   | PRI | NULL           | auto_increment |
 * ipb_address         | tinyblob         | NO   | MUL | NULL           |                |
 * ipb_user            | int(10) unsigned | NO   | MUL | 0              |                |
 * ipb_by              | int(10) unsigned | NO   |     | 0              |                |
 * ipb_by_text         | varbinary(255)   | NO   |     |                |                |
 * ipb_reason          | tinyblob         | NO   |     | NULL           |                |
 * ipb_timestamp       | binary(14)       | NO   | MUL |                |                |
 * ipb_auto            | tinyint(1)       | NO   |     | 0              |                |
 * ipb_anon_only       | tinyint(1)       | NO   |     | 0              |                |
 * ipb_create_account  | tinyint(1)       | NO   |     | 1              |                |
 * ipb_enable_autoblock | tinyint(1)      | NO   |     | 1              |                |
 * ipb_expiry          | varbinary(14)    | NO   | MUL |                |                |
 * ipb_range_start     | tinyblob         | NO   | MUL | NULL           |                |
 * ipb_range_end       | tinyblob         | NO   |     | NULL           |                |
 * ipb_deleted         | tinyint(1)       | NO   |     | 0              |                |
 * ipb_block_email     | tinyint(1)       | NO   |     | 0              |                |
 * ipb_allow_usertalk  | tinyint(1)       | NO   |     | 0              |                |

The fields are:

Some of this information was adapted from schema.doc.
 * ipb_id : Primary key, introduced for privacy.
 * ipb_address : Blocked IP address in dotted-quad form or user name.
 * ipb_user : Blocked user ID or 0 for IP blocks.
 * ipb_by : User ID of the administrator who made the block.
 * ipb_by_text : Text username of the administrator who made the block.
 * ipb_reason : Reason for the block given by the administrator.
 * ipb_timestamp : Creation (or refresh) date in standard YMDHMS form.
 * ipb_auto : Indicates that the IP address was banned because a banned user accessed a page through it. If this is 1, ipb_address will be hidden.
 * ipb_anon_only : If set to 1, the block only applies to logged out users.
 * ipb_create_account : Prevents account creation from matching IP addresses.
 * ipb_enable_autoblock : Enables autoblock on the block.
 * ipb_expiry : Expiry time set by the administrator at the time of the block.
 * ipb_range_start : The first IP in an IP range block.
 * ipb_range_end : The last IP in an IP range block.
 * ipb_deleted : Allows the entry to be flagged, hiding it from users and sysops.
 * ipb_block_email : Prevents the user from accessing Special:Emailuser
 * ipb_allow_usertalk : Prevents a blocked user from editing their talk page.

Related pages: range blocks, admininstrator's guide to blocking, bans, bans and blocks.

DESCRIBE ipblocks; in MediaWiki 1.8 gives the following: ++-+--+-+-++ ++-+--+-+-++ ++-+--+-+-++
 * Field             | Type            | Null | Key | Default | Extra          |
 * ipb_id            | int(8)          | NO   | PRI | NULL    | auto_increment |
 * ipb_address       | tinyblob        | NO   | MUL | NULL    |                |
 * ipb_user          | int(8) unsigned | NO   | MUL | 0       |                |
 * ipb_by            | int(8) unsigned | NO   |     | 0       |                |
 * ipb_reason        | tinyblob        | NO   |     | NULL    |                |
 * ipb_timestamp     | char(14)        | NO   | MUL | NULL    |                |
 * ipb_auto          | tinyint(1)      | NO   |     | 0       |                |
 * ipb_anon_only     | tinyint(1)      | NO   |     | 0       |                |
 * ipb_create_account | tinyint(1)     | NO   |     | 1       |                |
 * ipb_expiry        | char(14)        | NO   | MUL | NULL    |                |
 * ipb_range_start   | tinyblob        | NO   | MUL | NULL    |                |
 * ipb_range_end     | tinyblob        | NO   |     | NULL    |                |

+--+-+--+-+-++ +--+-+--+-+-++ +--+-+--+-+-++
 * Field               | Type            | Null | Key | Default | Extra          |
 * ipb_id              | int(8)          | NO   | PRI | NULL    | auto_increment |
 * ipb_address         | tinyblob        | NO   | MUL | NULL    |                |
 * ipb_user            | int(8) unsigned | NO   | MUL | 0       |                |
 * ipb_by              | int(8) unsigned | NO   |     | 0       |                |
 * ipb_reason          | tinyblob        | NO   |     | NULL    |                |
 * ipb_timestamp       | char(14)        | NO   | MUL | NULL    |                |
 * ipb_auto            | tinyint(1)      | NO   |     | 0       |                |
 * ipb_anon_only       | tinyint(1)      | NO   |     | 0       |                |
 * ipb_create_account  | tinyint(1)      | NO   |     | 1       |                |
 * ipb_enable_autoblock | tinyint(1)     | NO   |     | 1       |                |
 * ipb_expiry          | char(14)        | NO   | MUL | NULL    |                |
 * ipb_range_start     | tinyblob        | NO   | MUL | NULL    |                |
 * ipb_range_end       | tinyblob        | NO   |     | NULL    |                |

+--+-+--+-+-++ +--+-+--+-+-++ +--+-+--+-+-++
 * Field               | Type            | Null | Key | Default | Extra          |
 * ipb_id              | int(11)         | NO   | PRI | NULL    | auto_increment |
 * ipb_address         | tinyblob        | NO   | MUL | NULL    |                |
 * ipb_user            | int(10) unsigned| NO   | MUL | 0       |                |
 * ipb_by              | int(10) unsigned| NO   |     | 0       |                |
 * ipb_reason          | tinyblob        | NO   |     | NULL    |                |
 * ipb_timestamp       | binary(14)      | NO   | MUL | NULL    |                |
 * ipb_auto            | tinyint(1)      | NO   |     | 0       |                |
 * ipb_anon_only       | tinyint(1)      | NO   |     | 0       |                |
 * ipb_create_account  | tinyint(1)      | NO   |     | 1       |                |
 * ipb_enable_autoblock | tinyint(1)     | NO   |     | 1       |                |
 * ipb_expiry          | varbinary(14)   | NO   | MUL | NULL    |                |
 * ipb_range_start     | tinyblob        | NO   | MUL | NULL    |                |
 * ipb_range_end       | tinyblob        | NO   |     | NULL    |                |
 * ipb_deleted         | tinyint(1)      | NO   |     | NULL    |                |
 * ipb_block_email     | tinyint(1)      | NO   |     | NULL    |                |

+--+-+--+-+-++ +--+-+--+-+-++ +--+-+--+-+-++
 * Field               | Type            | Null | Key | Default | Extra          |
 * ipb_id              | int(8)          | NO   | PRI | NULL    | auto_increment |
 * ipb_address         | tinyblob        | NO   | MUL | NULL    |                |
 * ipb_user            | int(8) unsigned | NO   | MUL | 0       |                |
 * ipb_by              | int(8) unsigned | NO   |     | 0       |                |
 * ipb_reason          | tinyblob        | NO   |     | NULL    |                |
 * ipb_timestamp       | char(14)        | NO   | MUL | NULL    |                |
 * ipb_auto            | tinyint(1)      | NO   |     | 0       |                |
 * ipb_anon_only       | tinyint(1)      | NO   |     | 0       |                |
 * ipb_create_account  | tinyint(1)      | NO   |     | 1       |                |
 * ipb_enable_autoblock | tinyint(1)     | NO   |     | 1       |                |
 * ipb_expiry          | char(14)        | NO   | MUL | NULL    |                |
 * ipb_range_start     | tinyblob        | NO   | MUL | NULL    |                |
 * ipb_range_end       | tinyblob        | NO   |     | NULL    |                |
 * ipb_deleted         | tinyint(1)      | NO   |     | NULL    |                |
 * ipb_block_email     | tinyint(4)      | NO   |     | NULL    |                |

+--+--+--+-+++ +--+--+--+-+++ +--+--+--+-+++
 * Field               | Type             | Null | Key | Default        | Extra          |
 * ipb_id              | int(11)          | NO   | PRI | NULL           | auto_increment |
 * ipb_address         | tinyblob         | NO   | MUL | NULL           |                |
 * ipb_user            | int(10) unsigned | NO   | MUL | 0              |                |
 * ipb_by              | int(10) unsigned | NO   |     | 0              |                |
 * ipb_by_text         | varchar(255)     | NO   |     |                |                |
 * ipb_reason          | tinyblob         | NO   |     | NULL           |                |
 * ipb_timestamp       | binary(14)       | NO   | MUL |                |                |
 * ipb_auto            | tinyint(1)       | NO   |     | 0              |                |
 * ipb_anon_only       | tinyint(1)       | NO   |     | 0              |                |
 * ipb_create_account  | tinyint(1)       | NO   |     | 1              |                |
 * ipb_enable_autoblock | tinyint(1)      | NO   |     | 1              |                |
 * ipb_expiry          | varbinary(14)    | NO   | MUL |                |                |
 * ipb_range_start     | tinyblob         | NO   | MUL | NULL           |                |
 * ipb_range_end       | tinyblob         | NO   |     | NULL           |                |
 * ipb_deleted         | tinyint(1)       | NO   |     | 0              |                |
 * ipb_block_email     | tinyint(1)       | NO   |     | 0              |                |