How to Build a Location-Based Hierarchy in SQL | Recursive Query Tutorial
"In this video, we'll dive deep into SQL to build a hierarchy based on location data. We'll start by creating a table to store locations from continents to cities and then write a recursive query to display this hierarchy in a clear, ordered format. Whether you're managing a global retail business or just learning SQL, this tutorial will guide you through handling hierarchical data in your database. Don't forget to like, share, and subscribe for more SQL tutorials!"
This approach ensures that the viewer gets a clear understanding of how to manage and display hierarchical data using SQL. The recursive CTE method is particularly powerful for handling such data, and the video will provide a practical demonstration.
--You are employed by a retail company that has stores across India and overseas.
Your manager has now requested that you present the hierarchy according to location,
beginning with the name of the continent, as an ad hoc task. Please refine the query and show the outcomes.
CREATE TABLE Locations (
ID INT PRIMARY KEY,
Name VARCHAR(100),
ParentID INT
);
INSERT INTO Locations (ID, Name, ParentID)
VALUES
(1, 'World', NULL), -- Top-level node
(2, 'Asia', 1), -- Continent under 'World'
(3, 'Europe', 1), -- Continent under 'World'
(4, 'India', 2), -- Country under 'Asia'
(5, 'Japan', 2), -- Country under 'Asia'
(6, 'Germany', 3), -- Country under 'Europe'
(7, 'France', 3), -- Country under 'Europe'
(8, 'Delhi', 4), -- City under 'India'
(9, 'Tokyo', 5), -- City under 'Japan'
(10, 'Berlin', 6), -- City under 'Germany'
(11, 'Paris', 7); -- City under 'France'
select * from Locations
with CTE as (
select id,name,parentid, 1 As Level,cast((Name) as varchar(max)) as hierarchy
from Locations t1
where parentid is null
union all
select t2.id,t2.name,t2.parentid, cte.level+1 as level, cast((cte.hierarchy +'*** '+ t2.name) as varchar(max)) as hierarchy
from Locations t2 join cte on t2.parentid=cte.id)
select * from cte
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