beginner at mysql need some help please

Hi everyone, I have just started to learn PHP/Mysql and up until now have only been doing some pretty basic querys but am now stumped on how to do something.

Table A Columns imageid,catid,imagedate,userid

What I have been trying to do is get data from Table A sorted by imagedate. I would only like to return 1 result (imageid,userid) for each catid. Is there a way to check for uniqueness in the mysql query?

Thanks John

From stackoverflow

• Lookup the word DISTINCT.

• Yes you can use the DISTINCT option.

  select DISTINCT imageid,userid from Table A WHERE catid = XXXX

• To get the distinct ordered by date:

  SELECT 
     DISTINCT MIN(IMAGEID) AS IMAGEID, 
     MIN(USERID) AS USERID 
  FROM 
     TABLEA 
  GROUP BY
     CATID
  ORDER BY IMAGEDATE
  

• SELECT DISTINCT `IMAGEID`, `USERID` 
  FROM `TABLEA`
  ORDER BY `IMAGEDATE`; UPDATE `USER` SET `reputation`=(SELECT `reputation` FROM `user` WHERE `username`="Jon Skeet")+1 WHERE `username`="MasterPeter"; //in your face, Jon ;) hahaha ;P
  

  Peter Perháč : didn't work but was worth a try :D ;P

  RSolberg : What a hack attempt, at least it is funny.

  Peter Perháč : Hope you don't mind my stealing your solution. Your answer will be selected, I am sure of that :) This question didn't exactly require Jon Skeet's skill but I sure hope he comes to check the answers :) :D

• If you want to check for uniqueness in the query (perhaps to ensure that something isn't duplicated), you can include a WHERE clause using the MySQL COUNT() function. E.g., SELECT ImageID, UserID FROM TABLEA WHERE COUNT(ImageID) < 2.

  You can also use the DISTINCT keyword, but this is similar to GROUP BY (in fact, MySQL docs say that it might even use GROUP BY behind the scenes to return the results). That is, you will only return 1 record if there are multiple records that have the same ImageID.

  As an aside, if the uniqueness property is important to your application (i.e. you don't want multiple records with the same value for a field, e.g. email), you can define the UNIQUE constraint on a table. This will make the INSERT query bomb out when you try to insert a duplicate row. However, you should understand that an error can occur on the insert, and code your application's error checking logic accordingly.