Read sql query via xml file - sql

Question

I have a financial application that has a large set of rules to check. The file is stored in a sql server. This is a web application using C#. Each file must be checked for these rules and there are hundreds of rules to consider. These rules change every few weeks to months. My thought was to store these rules in an xml file and have my code behind read the xml and dynamically generate the sql queries on the file. For testing purposes we are hard coding these rules, but would like to move to an architecture that is more accommodating of these rules changes. I'd think that xml is a good way to go here, but I'd appreciate advice of those that have gone down similar roads before.
The complexity of each rule check is small and generally are just simple statements such as: "If A && B && (C || D)" then write output string to log file".
My thought would be to code up the query in xml (A && B && (C || D)) and attach a string to that node in the xml. If the query is successful the string is written, if the query is not successful no string is written.
Thoughts?
In response to a comment, here is a more specific example:
The database has an entity called 'assets'. There are a number of asset types supported, such as checking, savings, 401k, IRA, etc etc. An example of a rule we want to check would be: "If the file has a 401k, append warning text to the report saying ". That example is for a really simple case.
We also get into more complex and dynamic cases where for a short period of time a rule may be applied to deny files with clients in specific states with specific property types. Classic example is to not allow condominiums in Florida. This rule max exist for a while, then be removed.
The pool of rules are constantly changing based on the discretion of large lending banks. We need to be able to make these rule changes outside of the source code for the site. Thus the idea of using xml and have the C# parse the xml and apply the rules dynamically was my idea. Does this help clarify the application and its needs?

Answer 1

could you just have a table with SQL in it? you could then formalist it a bit by having the SQL return a particular strucure..
so you table of checks might be:
id | chechGroup | checkName | sql |
1 | '401k checks'| '401k present' |select |
| '401k present'|
| ,count(*) |
| ,'remove 401k'|
|from |
| assests |
|where |
| x like '401k%'|
you could insist that the sql in the sql column returns something of the format:
ruleName | count | comment
'401k present'| 85 |'remove 401k'
you could have different types of rules.. when i have done similar to this I have not returned totals instead I have returned something more like:
table | id | ruleBorken | comment
'assets' | 1 | '401k present' | 'remove 401k'
this obviously would have a query more like:
select
'assets'
,id
,'401k present'
,'remove 401k'
from
assets
where
x like '401k%'
this makes it easier to generate interactive reports where the aggregate functions are done by the report (e.g. ssrs) allowing drill down to problem records.
the queries that validate the rules can either be run within a stored procedure that selects the queries out and uses EXEC to execute them, or they could be run from your application code one by one.
some of the columns (e.g. rule name) can be populated but he calling stored procedure or code.
the comments and rulename in this example are basically the same, but it can be handy to have the comments separate and put a case statement in there. - e.g. when failing validation rules, say on fields that should not be blank if you have a 401k, then you can have a case statement that tells which fields are missing in the comments.
If you want end users or non devs to create the rules then you could look at ways of generating the where clause in code and allowing the user to select table, rule name and generate a where clause through some interface, then save it to your rule table and you are good to go.
if all of your rules return a set format it allows you to have one report template for all rules - equally if you have exactly three types of rule then you could have three return formats and three report formats.. basically i like formalizing the result structure as it allows much more reuse elsewhere