Question

Given the simple data structure:

ID    |    Category_Name    |    Parent_ID

Example:

1          Cars                    0
2          Boxes                   0
3          Lamborghinis            1
4          VW Camper Vans          1
5          Big Boxes               2
6          Small Boxes             2
7          Cereal Boxes            2
8          Broken Lambos           3
9          Yellow Ones             3
10         Rusty                   8
11         Milkshake Stained       8
12         Chocolate Flavour       11
13         Strawberry              11
14         Indiscernible Solution  11

Representing a simple tree navigation structure, what would programatically be the best way to retrieve the tree in a presentable format? Can we create an SQL statement to retrieve them ‘in order’?

Thanks for any help! If my approach is wrong, feel free to comment also.

I’m using SQL-Server 2000.

Answer 1

If you’re using SQL Server 2008 you might want to try out the new hierarchyid data type.

If you’re not then another way is to look into the nested sets model which works on all databases.

If you’re using SQL Server 2005 and up you can use recursive CTEs to retreive the tree structure.