Concatenate multiple rows to form one single row in SQL Server? - sql

Question

Overview
I need to build a description field that describes an entity. The data I am working with has the property description split for each individual key in my table. Below is an example of what the data looks like:
+------------+--------------------+----------+
| Key | Desc | Order_Id |
+------------+--------------------+----------+
| 5962417474 | Big Yellow Door | 14775 |
| 5962417474 | Orange Windows | 14776 |
| 5962417474 | Blue Triangle Roof | 14777 |
+------------+--------------------+----------+
Originally, I wrote a query using an aggregate function like so:
SELECT
[P].[KEY],
CONCAT (MIN([P].[Desc]), + ' ' + MAX([P].[Desc])) [PROPERTY_DESCRIPTION]
FROM [dbo].[PROP_DESC] [P]
WHERE [P].[KEY] = '5962417474'
GROUP BY [P].[KEY];
This worked great for two row entries but then I realized what if I have multiple records for a property description? So I wrote the following query to check if I had multiple property descriptions:
SELECT
[P].[KEY], COUNT([P].[KEY])
FROM [dbo].[PROP_DESC] [P]
GROUP BY [P].[KEY]
HAVING COUNT(*) > 2; -- Returns one record which is the above table result.
This gave me back a record with three descriptions so my original query will not work. How can I tackle this problem down when there are multiple fields?
Desired Output
+------------+---------------------------------------------------+----------+
| Key | Desc | Order_Id |
+------------+---------------------------------------------------+----------+
| 5962417474 | Big Yellow Door Orange Windows Blue Triangle Roof | 14775 |
+------------+---------------------------------------------------+----------+

Answer 1

It depends on what SQL language you're using, but you'll want to use some kind of group concat / array agg function. Eg:
SELECT
Key,
STRING_AGG(desc, ', ')
FROM TABLE
GROUP BY Key;

Answer 2

I have solved my problem with the following query for those that have the same problem and do not have access to STRING_AGG which is introduced in SQL Server 2017:
SELECT
[P].[KEY],
[PROPERTY_DESCRIPTION] = STUFF((
SELECT ' ' + [P2].[DESC]
FROM [dbo].[PROP_DESC] [P2]
WHERE [P].[KEY] = [P2].[KEY]
FOR XML PATH(''), TYPE).value('.', 'VARCHAR(MAX)'), 1, 1, '')
FROM [dbo].[PROP_DESC] [P]
WHERE [P].[KEY] = '5962417474'
GROUP BY [P].[KEY]

Answer 3

There are many ways to do it in SQL server:
Below is one way:
SELECT key
,STUFF((SELECT '| ' + CAST(prop_desc AS VARCHAR(MAX)) [text()]
FROM PROP_DESC
WHERE key = t.key
FOR XML PATH(''), TYPE)
.value('.','NVARCHAR(MAX)'),1,2,' ') prop_desc
FROM PROP_DESC t
GROUP BY key