Click here to Skip to main content
Click here to Skip to main content

Tagged as

Stupid CTE tricks -- string concatenation

, 25 Dec 2011 CPOL
Rate this:
Please Sign up or sign in to vote.
Concatenating values from multiple rows into one string value via a Common Table Expression
If you have a table like:
Make    Model
<hr />
Toyota  Yaris
Toyota  Corrolla
Ford    Pinto
Ford    Model A
Ford    Thunderbird
Nash    Rambler

and you want something like:
Make    Models                          Count
<hr />
Ford    Thunderbird , Pinto , Model A   3
Nash    Rambler                         1
Toyota  Yaris , Corrolla                2

you'll need to write some code -- SQL Server doesn't have that built in (yet).
You can write a function to do it, you can write a custom CLR aggregator to do it, but I wanted to see if I could use a Common Table Expression to do it.

The following is such a CTE:
  , COUNT(*) [Count]
  , MAX(Model) Models
  , 0 [Rank]
  FROM MakeModel
  SELECT cte.Make
  , cte.[Count]
  , Models + N' , ' + Model
  , [Rank] + 1
  FROM cte
  INNER JOIN MakeModel
  ON cte.Make=MakeModel.Make
  AND cte.Models NOT LIKE '%' + Model + '%'
  AND cte.[Rank]<cte.[Count]
SELECT Make,MAX(Models) Models,MAX([Count]) [Count] FROM cte GROUP BY Make ORDER BY Make

0) You may need to CONVERT your values to NVARCHAR(MAX)
1) You may need to protect against NULL values
2) I don't think this will scale well
3) I can't think of a way to get the values listed ascending rather than descending

This was mainly an interesting exercise, I don't expect to use it in production systems.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Software Developer (Senior)
United States United States
BSCS 1992 Wentworth Institute of Technology

Originally from the Boston (MA) area. Lived in SoCal for a while. Now in the Phoenix (AZ) area.

OpenVMS enthusiast, ISO 8601 evangelist, photographer, opinionated SOB, acknowledged contrarian


"If you need help knowing what to think, let me know and I'll tell you." -- Jeffrey Snover [MSFT]

"Typing is no substitute for thinking." -- R.W. Hamming

"I find it appalling that you can become a programmer with less training than it takes to become a plumber." -- Bjarne Stroustrup

ZagNut’s Law: Arrogance is inversely proportional to ability.

"Well blow me sideways with a plastic marionette. I've just learned something new - and if I could award you a 100 for that post I would. Way to go you keyboard lovegod you." -- Pete O'Hanlon

"linq'ish" sounds like "inept" in German -- Andreas Gieriet

"Things would be different if I ran the zoo." -- Dr. Seuss

"Wrong is evil, and it must be defeated." – Jeff Ello

"A good designer must rely on experience, on precise, logical thinking, and on pedantic exactness." -- Nigel Shaw

“It’s always easier to do it the hard way.” -- Blackhart

“If Unix wasn’t so bad that you can’t give it away, Bill Gates would never have succeeded in selling Windows.” -- Blackhart

"Omit needless local variables." -- Strunk... had he taught programming

"We learn more from our mistakes than we do from getting it right the first time."

My first rule of debugging: "If you get a different error message, you're making progress."

My golden rule of database management: "Do not unto others' databases as you would not have done unto yours."

My general rule of software development: "Design should be top-down, but implementation should be bottom-up."

Comments and Discussions

GeneralFor ordering ascending, try changing AND cte.[Rank] < ct... Pinmemberjsc423-Jan-12 2:11 
For ordering ascending, try changing
AND cte.[Rank] < cte.[Count]
AND cte.[Rank] > cte.[Count]

or try changing
, Models + N' , ' + Model
, Model + N' , ' + Models

I don't have SQL Server, so I cannot test either of these two possible solutions. I would be interested to know if either / both work.
General0) your input tables do have to be converted to nvarchar(max... PinmemberDaniel Gidman21-Dec-11 8:57 
GeneralRe: 0) I know the ones shown don't 1) I think they might, but I ... PinmemberPIEBALDconsult21-Dec-11 17:48 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Terms of Use | Mobile
Web03 | 2.8.150331.1 | Last Updated 25 Dec 2011
Article Copyright 2011 by PIEBALDconsult
Everything else Copyright © CodeProject, 1999-2015
Layout: fixed | fluid