Question

I have Plan table that has a one to many relationship with a Price table.
(1 plan can have many prices)

However the problem is I have another table called “StandardPrices” that holds the names of all the prices (The reason for this is I want to be able to add or remove prices at any time)

 Plan Table:
 ID int primary key,
 plan Name varchar(200),
 ...

 PriceTable:
 ID int primary key,
 PlanId int foreign key references plan(ID)
 PriceName ID foreign key standardprices(id)

 StandardPrices:
 ID int primary key,
 PriceName varchar(200),
 DefaultPrice money

So whenever a plan is created, it automatically creates a List of all the prices in the StandardPrice list (with default values).

The problem I have, Is I need, whenever I create a new StandardPrice, it automatically checks if that price exists in every plan, and if it doesnt, create an entry in the price table for that planid.

I use Stored procedures and thought the best way to do this would be through SQL.

When StandardPrices are created:

   begin      
   insert into StandardPrices (PriceName, Defaultprice)
       values (@priceName, @DefaultPrice)
   end

   begin
   //list all plans.
   //cross reference PriceTable to see if plan exists
   //if not insert priceplan with default value
   end

I am a bit confused how i can implement such a sql command?

Answer 1

I think it looks something like this:

insert into PriceTable (PlanId, PriceName)
select PlanId, @priceName
from Plan
where not exists 
  (select null from PriceTable where PriceTable.PlanId = Plan.PlanId)

And you should probably do this as part of an INSERT trigger on your database.