i've a old database where i store the data of the holidays and dates in which they are celebrated.. id country hdate description link 1 Afghanistan 2008-01-19 Ashura ashura 2 Albania 2008-01-01 New Year Day new-year the flaws in the above structure is that, i repeat the data other than date for every festival and every year and every country.. For example, I store a new date for 2009 for ashura and afghanistan .. I tried to limit the redundancy and split the tables as countries (id,name) holidays (id, holiday, celebrated_by, link) // celebrated_by will store the id's of countries separated by ',' holiday_dates (holiday_id, date, year) // date will the full date and year will be as 2008 or 2009 Now i have some problems with the structure too.. consider that i store the holiday like Independence day , its common for more countries but will have different dates. so how to handle this and and the link will have to be different too.. And i need to list the countries which celebrates the same holiday and also when i describe about a single holiday i need to list all the other holidays that country would be celebrating.. And the most of all , i already have huge amount of data in the old tables and i need to split it to the new one once the new design is finalized... Any ideas?