CONCAT with GROUP_CONCAT in mysql

Question

So I have looked everywhere for an answer to this, but so far no luck. Any help is much appreciated. I am new to mysql (transferring from a filemaker pro background).

I have a database where I keep information for prospects for our business. I have a question about listing information for our users to see. The INQUIRY table holds the information for each inquiry (i.e. date inquiry came in, status of the inquiry, etc.). The PROSPECT table holds the information on each prospect (potential client) (i.e. first name, last name, age, etc.). A third table, INQUIRYNOTES, hold information on our contacts with the prospect (i.e. next contact date, notes, next action, etc.). Each of these tables are related with the key inquiryID.

Each day a user will come to a screen where they will be presented with the leads/inquiries that he/she will follow up on for that day which are those inquiries who's action date is less than or equal to today. I want the list to contain the inquiryID, listed names of all prospects related to that inquiryID (max 2), and the action date.

Here is what I've tried so far:

SELECT inquiry.inquiryID,
   CASE WHEN prospect.lastName = '' THEN prospect.firstName
   WHEN prospect.firstName = '' THEN prospect.lastName
   ELSE CONCAT(prospect.lastName, ', ',prospect.firstName) END as fullName, inquiryNote.actionDate
FROM inquiry, prospect, inquiryNote
WHERE inquiry.inquiryID = prospect.inquiryID
AND inquiry.inquiryID = inquirynote.inquiryID
AND inquirynote.actionDate != \"0000-00-00\"
AND actionDate <= \"".date("Y-m-d")."\"
GROUP BY inquiryID ORDER BY actionDate";

This returns the information that I am looking for, but it only lists one of the prospect (even if there are 2 for the inquiry).

Next I tried putting the GROUP_CONCAT(firstname) in this and it gave me a list of the first names of the prospect listed in a row separated by commas (I'm getting closer). Then I tried GROUP_CONCAT(last name, ', ', firstname) and then GROUP_CONCAT(lastname,firstname), but again it would only list one prospect, not the multiple prospects separated by commas.

I want the variable that I named fullName in the code above to be included in the GROUP_CONCAT so that in the rows returned I see a list of all prospect related to an inquiry listed and divided by a comma.

I want the table in the webpage I have created to have these columns:

inquiryID | prospects name(s) (last name first) | Next Action Date

Again so far I can only seem to get:

inquiryID | 1 prospect name | Next Action Date

The solution could be something easy, but since I am new to mysql I am lost.

Please let me know if you need more detail.

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UPDATE WITH SOLUTION, BUT SIMILAR QUESTION AT THE END

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The problem was that some of the first name and last name fields had NULL values. Apparently, GROUP_CONCAT will now work with null values. This is the query that I ended with that worked once I got rid of all of the NULL values:

SELECT 
  inquiry.inquiryID, 
  inquiry.initialDate,
  inquiryNote.actionDate,
  GROUP_CONCAT(DISTINCT
    CONCAT(
      CASE WHEN prospect.lastName = '' THEN prospect.firstName
      WHEN prospect.firstName = '' THEN prospect.lastName
       ELSE CONCAT(
        prospect.firstName, ' ',prospect.lastName
      ) END
    ) SEPARATOR ', '
  ) AS prospectList,

GROUP_CONCAT(DISTINCT
    CONCAT(
      CASE WHEN influencer.lastName = '' THEN influencer.firstName
      WHEN influencer.firstName = '' THEN influencer.lastName
      ELSE CONCAT(
        influencer.firstName, ' ',influencer.lastName
      ) END
    ) SEPARATOR ', '
  ) AS influencerList

FROM inquiry, prospect, inquiryNote, influencer WHERE inquiry.inquiryID = prospect.inquiryID
AND inquiry.inquiryID = inquirynote.inquiryID
AND inquiry.inquiryID = influencer.inquiryID
AND inquirynote.actionDate != "0000-00-00" AND actionDate <= "2011-09-22"
GROUP BY inquiryID
ORDER BY actionDate;

So the final question is, can I make GROUP_CONCAT work even when it encounters NULL values?

Answer 1

You can COALESCE the columns in case the contain NULLs:

COALESCE(lastname, '') would return an empty string if lastname was null, or whatever the value of lastname is if it is not.

Answer 2

GROUP_CONCAT simply ignores(skips) NULL values http://thinkdiff.net/mysql/mysql-the-group_concat-function/