Question

I have two dropdownlist one for project and 2nd for category.
I have a to select ddproject where i get id, based on this id i have to populate ddcategory.
Table Sturcture SQL FIDDLE

Here simple query if i select ProjectOne from my dropdownlist

select  id,name from tbcategory where id in(1,2)  

But my problem is i don’t know how many value will be there in the in condition.

C#:
1st i split column name categoryid and get values later what to do am confused.
Also let me know whether am doing in right way or any other alernative way to achive this

Edited:
Or should i change my table structure, if yes then what schema to be ?

Answer 1

According to your data, there is a many : many relationship between Category and Project. You therefore need to model another Many:Many table to hold data modelling this relationship.

SQL Fiddle Here

Firstly, create a new table to hold the Many:Many relationship between Category and Project:

create table tbProjectCategory
(
  tbProjectId INT,
  tbCategoryId INT
);

Then, remove the string comma delimited relationship in tbProject – this isn’t useful. Instead, insert the links into the Many Many table. e.g.:

insert into tbProjectCategory(tbProjectId, tbCategoryId) values (1, 1), (1, 2);

Will link project 1 to category 1 and 2.

Then, to find all the Categories for Project 1, you need to join through the Many:Many link table, filtering by the Project Id:

select  cat.id, cat.name 
  from tbcategory cat
  inner join tbProjectCategory prjcat
  on prjcat.tbCategoryId = cat.id
  where prjCat.tbProjectId = 1;

I’ve also removed your identity column for brevity’s sake – it makes it easier to know which data records are linked.