Experienced an error #1060 - Duplicate of Column 'forum_enabled' - mysql

Question

What is wrong with this?
ALTER TABLE `groups`
ADD COLUMN `forum_enabled` enum('0','1') CHARACTER SET latin1 COLLATE
latin1_swedish_ci NOT NULL DEFAULT '0' AFTER `admindeco`;
ALTER TABLE `user_badges`
ADD UNIQUE INDEX `user_id, badge_id`;
ALTER TABLE `furniture`
ADD COLUMN`behaviour_data` int(11) NOT NULL DEFAULT 0 AFTER
`interaction_type`;
ALTER TABLE `users`
MODIFY COLUMN `rank_vip` int(1) NULL DEFAULT 1 AFTER `rank`;
ALTER TABLE `server_settings`
CHANGE COLUMN `variable` `key` varchar(255) CHARACTER SET latin1 COLLATE
latin1_swedish_ci NOT NULL DEFAULT 'server.variable' FIRST ;
ALTER TABLE `catalog_deals`
DROP COLUMN `page_id`,
DROP COLUMN `cost_credits`,
DROP COLUMN `cost_pixels`,
MODIFY COLUMN `items` text CHARACTER SET latin1 COLLATE
latin1_swedish_ci
NOT NULL AFTER `id`,
ADD COLUMN `room_id` int(11) NOT NULL AFTER `name`;
SET FOREIGN_KEY_CHECKS=0;
I am getting following error:
SQL query: ALTER TABLE groups ADD COLUMN forum_enabled ENUM( '0', '1' ) CHARACTER SET latin1 COLLATE latin1_swedish_ci NOT NULL DEFAULT '0' AFTER admindeco ; MySQL said: Documentation #1060 - Duplicate column name 'forum_enabled'

Answer 1

From the error message, it seems like the column you are trying to add in the first statement already exists in the table.
A simple solution is to DROP the column before you add it, like :
ALTER TABLE `groups`
DROP COLUMN `forum_enabled`;
This can be combined with the ADD command in a single statement, like :
ALTER TABLE `groups`
DROP COLUMN `forum_enabled`,
ADD COLUMN `forum_enabled` enum('0','1') ...
;
It is also possible to dynamically check if a column exists, then drop it if neede, like :
IF EXISTS (
SELECT 1
FROM information_schema.columns
WHERE
table_name = 'groups'
AND column_name = 'forum_enabled'
AND table_schema = DATABASE()
) THEN
ALTER TABLE `groups`
DROP COLUMN `forum_enabled`;
END IF;