Click here to Skip to main content
15,877,168 members
Articles / Database Development / SQL Server

Stupid CTE tricks -- string concatenation

Rate me:
Please Sign up or sign in to vote.
4.67/5 (5 votes)
25 Dec 2011CPOL 39.6K   9   3
Concatenating values from multiple rows into one string value via a Common Table Expression
If you have a table like:

Make    Model
------- -----------
Toyota  Yaris
Toyota  Corrolla
Ford    Pinto
Ford    Model A
Ford    Thunderbird
Nash    Rambler

and you want something like:

Make    Models                          Count
------- ------------------------------- -----
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)

Written By
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 pedant and contrarian


"I would be looking for better tekkies, too. Yours are broken." -- Paul Pedant

"Using fewer technologies is better than using more." -- Rico Mariani

"Good code is its own best documentation. As you’re about to add a comment, ask yourself, ‘How can I improve the code so that this comment isn’t needed?’" -- Steve McConnell

"Every time you write a comment, you should grimace and feel the failure of your ability of expression." -- Unknown

"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

"Use vertical and horizontal whitespace generously. Generally, all binary operators except '.' and '->' should be separated from their operands by blanks."

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

Comments and Discussions

GeneralFor ordering ascending, try changing AND cte.[Rank] < ct... Pin
jsc423-Jan-12 1:11
professionaljsc423-Jan-12 1:11 
General0) your input tables do have to be converted to nvarchar(max... Pin
Daniel Gidman21-Dec-11 7:57
professionalDaniel Gidman21-Dec-11 7:57 
GeneralRe: 0) I know the ones shown don't 1) I think they might, but I ... Pin
PIEBALDconsult21-Dec-11 16:48
mvePIEBALDconsult21-Dec-11 16:48 

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

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