The 'historic_races' table in the database includes a field called "added money". This is the total amount of prize money put up by the racing authorities. The actual prizes paid comprise this plus the nomination / entry fees paid by owners of the horses running for each race. The latter only represents a very small percentage of the total so the "added money" field is a very good guide to the overall value of the race.
The "daily_races" table contains the "added money" but also individual prize values for the winner and all placed horses where a prize is awarded.
The "historic" table contains post-race information and is therefore a bit more reliable - for example, it will only list British and Irish races that were actually run. The "daily" table contains pre-race information and therefore includes some races that did not actually take place (i.e. abandoned meetings, etc.), plus a few big races from outside GB and Ireland.
Be aware of currency differences in prize money data. Races in Great Britain (that is England, Scotland and Wales) races pay prizes in GBP (pounds sterling). Races in Ireland (that is Northern Ireland or the Republic of Ireland (referred to as "Eire" in the database)) pay prizes in EUR (Euros)
All data goes back to 1 January 2003.
Hope this helps
