c# and sqlserver how to get data from second table if exists

Question

After some advice if there is a simpler and more efficient way of what I'm about to do....

I have a table with product data in sqlserver then a frontend in asp.net c#, this has export to excel, txt file options and publish to API's.

now I need to build in that we hold certain fields like product description in a different format for certain customers,

so product table is like

PT_PRODUCT|PT_DESC              |PT_SIZE
ABC123    |Super Cool Ice-Cream |small

but then for 'Customer 1' the product description needs to be 'Ice Cool Lollypop'

I was going to create a class for 'Product' in my application and fill that with the values from the main table,

then query a second table that would look like this,

CUST |PRODUCT  | FIELD_ID | FIELD_VAL
CU1  |ABC123   |PT_DESC   |Ice Cool Lollypop

and would run something like

select * from table2 where cust='CA1' and product='ABC123'

for(int i=0;i< ds.tables[0].rows.count;i++)
{
   switch(ds.Tables[0].Rows[i]["FIELD_ID"])
   {
    case "PT_DESC":
    ClassProd.DESC = ds.Tables[0].Rows[i]["FIELD_VAL");
    //and so on updating the class
   }
}

the use the updated class to update the customers site via the API or exporting to excel ect,

now for the slight curve-ball, there may be around 20+ fields that need to be overridden by the customers data, also going down this route I will be dictating the fields that can be overridden, so was wondering if there was a way of doing this in the original sql select.

Answer 1

You could create a stored procedure and forget about having to do any of the C# to get the customer's custom products.

This left joins the CustomerProducts table on the Product Id and the Customer Id. If it is NULL, it didn't find a customer product description so it will use the default one from the Products table. If it is NOT NULL, then it found a customer product description in CustomerProducts and uses that instead.

I don't know your schema exactly, but this is the gist:

CREATE PROCEDURE GetCustomerProducts
(
    @CustomerId VARCHAR(255),
    @ProductId VARCHAR(255)
)
AS
BEGIN
SELECT PRODUCT
    ,FIELD_ID
    ,CASE 
        WHEN cp.FIELD_VAL IS NOT NULL
            THEN cp.FIELD_VAL
        ELSE p.FIELD_VAL
        END AS FIELD_VAL
FROM Products p
LEFT JOIN CustProducts cp ON cp.PT_PRODUCT = p.PT_PRODUCT
    AND cp.CUST = @CustomerID
WHERE p.PT_PRODUCT = @ProductId
END

Then:

EXEC GetCustomerProducts @CustomerId = 'CU1', @ProductId = 'ABC123'