1. Add a column in a table
ALTER TABLE `ess` ADD `day` DATE NOT NULL COMMENT 'date of the day' AFTER `recid` , ADD UNIQUE ( `day` )
2. Or it can me similar to this also
ALTER TABLE `diary` ADD `duedate` DATE default "2010-01-01" COMMENT 'due date of the entry' AFTER `modified`
3. Third example
ALTER TABLE `diary_options` ADD `show_duedate` INT( 1 ) NOT NULL COMMENT 'to show duedate or not' AFTER `show_modified`
