SQL Server 2008: many-to-many relationship: Concatenation in SELECT query [duplicate] - sql

Question

This question already has answers here:
How to make a query with group_concat in sql server [duplicate]
(4 answers)
Closed 4 years ago.
There are 3 tables:
Project
Tool
LinkProjectTool
I need a query that lists everything in the Project table plus an extra column called ProjectTools. This column should contain a comma delimited string with all the tool names belonging to each project.
The data is:
Table Project:
ID Name Client
------------------------
0 table Anna
1 chair Bobby
2 workbench James
3 window Jenny
4 shelves Matthew
Table Tool:
ID Name
------------------------
0 hammer
1 measuring tape
2 pliers
3 scissors
4 spanner
5 saw
6 screwdriver
Table LinkProjectTool:
IDProject IDTool
-------------------
0 0
0 3
2 1
2 4
2 5
The result should be:
ID Name Client ProjectTools
-------------------------------------------------------------
0 table Anna hammer, scissors
1 chair Bobby
2 workbench James measuring tape, spanner, saw
3 window Jenny
4 shelves Matthew
Here are the queries I used to create these tables:
CREATE TABLE [dbo].[Project]
(
[ID] [int] NOT NULL,
[Name] [nvarchar](15) NOT NULL,
[Client] [nvarchar](15) NULL
)
INSERT INTO [dbo].[Project]
(ID, Name, Client)
VALUES
(0, 'table', 'Anna'),
(1, 'chair', 'Bobby'),
(2, 'workbench', 'James'),
(3, 'window', 'Jenny'),
(4, 'shelves', 'Matthew')
CREATE TABLE [dbo].[Tool](
[ID] [tinyint] IDENTITY(0,1) NOT NULL,
[Name] [nvarchar](30) NULL,
CONSTRAINT [PK_Tool] PRIMARY KEY CLUSTERED
(
[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
INSERT INTO [dbo].Tool
(Name)
VALUES
('hammer'),
('measuring tape'),
('pliers'),
('scissors'),
('spanner'),
('saw'),
('screwdriver')
CREATE TABLE [dbo].LinkProjectTool
(
[IDProject] [int] NOT NULL,
[IDTool] [tinyint] NULL
)
INSERT INTO [dbo].LinkProjectTool
(IDProject, IDTool)
VALUES
(0, 0),
(0, 3),
(2, 1),
(2, 4),
(2, 5)
Could you, please, help?
Thank you.

Answer 1

You can use STUFF function alongside with FOR XML (see this answer for a more detailed explanation on how they work).
Assuming you want the project tools to be separated by a comma and a blank space, you can use the following query:
SELECT DISTINCT p.ID, p.Name, p.Client,
ProjectTools = STUFF((
SELECT ', ' + t.Name
FROM Tool t
WHERE t.ID IN (SELECT IDTool FROM LinkProjectTool WHERE IdProject = p.ID)
FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(MAX)'), 1, 2, '')
FROM Project p LEFT OUTER JOIN LinkProjectTool lpt ON p.Id = lpt.IDProject
ORDER BY p.ID