Inserting default value as current date + 30 days in MySQL

How can I make a column's default value equal to the current date + 30 days in MySQL? For example开发者_运维技巧, if current date is 10-1-2011 then the column value must be inserted as 9-2-2011.

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If you're using MySQL >= 5.0, use a trigger:

CREATE TRIGGER setDefaultDate
    BEFORE INSERT ON tableName
    FOR EACH ROW
    SET NEW.date = ADDDATE(curdate(), INTERVAL 30 DAY);

The trigger will activate when you insert into tableName, setting date to now + 30 days. If your insert sets the date, it will override this default due to the BEFORE. The date is calculated using ADDDATE.