Storing search criteria in a database

I am working on an enhancement to a Flex dashboard that will allow the users to save searches. I'm using BlazeDS and Java/Spring/SpringJdbc on the server side. My question is this: how would you model a search that has one or more criteria, such as: - Value Date between 2009-10-01 and 2009-10-31 - Currency = 'USD' - Bank Name starts with 'First' My first stab at this is to divide the criteria into 3 types: - Numeric criteria - Date criteria - String criteria Each of the criteria types has a different set of comparison operators: - Numeric operators: =, >, >=, <, <=, <> - Date operators: Before, After, Between - String operators: Starts with, Ends with, contains I have codes to identify each of these operators. My object model is a SearchCriteria interface and 3 classes that implement it: NumericCriteria, DateCriteria, and StringCriteria All of these classes map to the same table with the following columns: ``` - SAVED_SEARCH_ID: id of the saved search - SEQ_NUM: criteria order. We want to load the criteria in the same order each time - CRITERIA_TYPE: Operator code. I can use this later to determine what kind of criteria this is. - FIELD: currency, valueDate, bank, etc - FIRST_VALUE_NUMERIC - SECOND_VALUE_NUMERIC - FIRST_VALUE_DATE - SECOND_VALUE_DATE - FIRST_VALUE_STRING - SECOND_VALUE_STRING ``` Is there a cleaner way to do this? I'm not crazy about the data model, but I can't find any resources on this topic... All comments are appreciated, no matter how cruel :)