top button
Flag Notify
    Connect to us
      Site Registration

Site Registration

Retrieve most recent of multiple rows

0 votes
268 views

I have a table which looks like this:

answer_id  q_id  answer  qscore_id  answer_timestamp
1          10    Male    3          **********
2          10    Male    3          **********
3          11    Male    3          **********
4          10    Male    3          **********
5          11    Male    3          **********
6          12    Male    3          **********
7          11    Male    3          **********

So I have multiple answers for the same questions (q_id). I want to be able to retrieve only ONE answer per question and that be the most recent answer.
There should be THREE rows returned, which are all the most recent answered for that q_id:

4          10    Male    3          **********
6          12    Male    3          **********
7          11    Male    3          **********
posted Mar 13, 2013 by Salil Agrawal

Share this question
Facebook Share Button Twitter Share Button LinkedIn Share Button

2 Answers

0 votes
 
Best answer

this is the data i tested on 

      AID        QID ANS             SCRID ATIMESTAMP
---------- ---------- ---------- ---------- ---------------------------------------------------------------------------

     1         10 male                3 13-MAR-13 02.03.20.000000 PM
     2         10 male                3 13-MAR-13 02.03.28.000000 PM
     3         11 male                3 13-MAR-13 02.03.33.000000 PM
     4         10 male                3 13-MAR-13 02.03.36.000000 PM
     5         11 male                3 13-MAR-13 02.03.41.000000 PM
     6         12 male                3 13-MAR-13 02.03.48.000000 PM
     7         11 male                3 13-MAR-13 02.04.04.000000 PM

7 rows selected.

select qid,max(atimestamp) from kkk where qid in (select distinct qid from kkk) group by qid;

      QID MAX(ATIMESTAMP)
---------- ---------------------------------------------------------------------------
    11 13-MAR-13 02.04.04.000000 PM
    10 13-MAR-13 02.03.36.000000 PM
    12 13-MAR-13 02.03.48.000000 PM
answer Mar 13, 2013 by anonymous
0 votes

select * from tab where anwer_timestamp in (select max(anwer_timestamp) from tab where q_id in (select distinct q_id from tab) group by q_id);

answer Mar 13, 2013 by anonymous
Similar Questions
0 votes
Foreign key on multiple columns

I'm trying to create a foreign key on two columns but getting error...

Here's what I tried:

CREATE TABLE test2 (
  ID INT NOT NULL AUTO_INCREMENT,  
  col1 INT NOT NULL,
  col2 INT NOT NULL, 
  PRIMARY KEY (ID),
  CONSTRAINT fk FOREIGN KEY (col1, col2)
                REFERENCES test1(ID, ID)
  ON UPDATE CASCADE
  ON DELETE RESTRICT
) ENGINE=InnoDB;

But I get ERROR 1005 (HY000): Can't create table 'DB.test2' (errno: 150)

0 votes
Mysql Cluster Sync-UP

I am running My-SQL in cluster mode with two machine. Want to know if mysql database get corrupted on one of the machine will it force the corruption on the other machine too or in this case sync between two mysql instances will stop after the corruption.

0 votes
Importing SQL dumps into MySQL through Command line

To source sqldump i can use the source command, but if I need to do the same stuff using command line without going to the sqlpromt, can I achieve that.

0 votes
Converting Mysql to mysql cluster

My site is using mysql and PHP, now for the scale purpose want to introduce mysql-cluster. Few questions are -
1. Do I need to change any code which is written in PHP.
2. What are the steps to convert mysql to mysql-cluster.

Appreciate the help.

...