Question

Mysql select query return one random record for each unique value from a field

Asked by: Kupsi

I have this table, and want to select one random item from two random usernames:

ID  -   Username   -   Item
1   -   Kupsi   -   Car
2   -   Kupsi   -   House
3   -   John    -   Cat
4   -   Ben     -   Car
5   -   Kupsi   -   Apple
6   -   John    -   Shirt
7   -    Ben    -    Hat
8    -   Mike    -    Glass


I want the results to be:
John - Shirt
Kupsi - Apple

or
Kupsi - Car
John - Cat

or
Mike - Glass
Kupsi - House

etc...

I don't want the result to be
Kupsi - House
Kupsi - Car

or
John - Cat
John - Shirt

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Asked On
2009-03-21 at 03:49:20ID24251757
Tags

mysql query

Topics

SQL Query Syntax

,

MySQL Server

Participating Experts
4
Points
500
Comments
13

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Answers

 

by: angelIIIPosted on 2009-03-21 at 04:08:58ID: 23946767

please try this:

select username, item
  from yourtable
 group by username
 order by RAND()  
 limit 2

                                              
1:
2:
3:
4:
5:

Select allOpen in new window

 

by: KupsiPosted on 2009-03-21 at 04:47:18ID: 23946862

I've tried that angellll...

The usernames are choosen randomly, but I get the same item every time a user is choosen. I want the items also to be randomly choosen.

 

by: theGhost_k8Posted on 2009-03-21 at 05:46:11ID: 23947038

seems like not possible !!

 

by: angelIIIPosted on 2009-03-21 at 06:45:12ID: 23947317

I would then do the below query, and in the front end application, get and display only the first row of each username (you loop all the rows, and only display a row the first time you get a username you have not fetched already.

select id, username, item
 from yourtable t
where t.username in ( 
select username
  from yourtable
 group by username
 order by RAND()  
 limit 2
)
order by RAND()

                                              
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:

Select allOpen in new window

 

by: racekPosted on 2009-03-21 at 10:23:15ID: 23948055

select a.username,  IF(MAX(FLOOR(1 + (RAND() *1)) = 1, a.item , b.tiem) as item
 from yourtable a JOIN yourtable b
WHERE
a.username = username and a.item <>  b.item  
group by 1;


 

by: racekPosted on 2009-03-21 at 10:24:14ID: 23948058

select a.username,  IF(MAX(FLOOR(1 + (RAND() *1)) = 1, a.item , b.tiem) as item
 from yourtable a JOIN yourtable b
WHERE a.username = b.username and a.item <>  b.item  
group by 1;

 

by: psadacPosted on 2009-03-21 at 13:09:04ID: 23948638

SELECT
    *
FROM (
    SELECT
        username
        , item
    FROM
        yourtable
    ORDER BY
        RAND()) AS tmp
 GROUP BY
    username
ORDER BY
    RAND()
LIMIT
    2;

                                              
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:

Select allOpen in new window

 

by: racekPosted on 2009-03-21 at 16:12:32ID: 23949386

select a.username,
      IF(MAX(FLOOR(1 + (RAND()) *2)) = 1,
      a.item , b.item) as item
 from tst a JOIN tst b
WHERE a.username = b.username and a.item <>  b.item
group by 1;

 

by: racekPosted on 2009-03-22 at 09:36:00ID: 23952168

SELECT a.username,
       IF(MAX(FLOOR(1 + (RAND()) * 2)) = 1
          and NOT a.item IS NULL, a.item,
       IF(b.item IS NOT NULL, b.item, a.item)) AS item
  FROM    yourtable a   LEFT JOIN  yourtable b
       ON a.username = b.username AND a.item <> b.item
GROUP BY 1
ORDER BY RAND()
 LIMIT 2;

 

by: racekPosted on 2009-03-22 at 10:42:14ID: 23952442

this one ic covering cases with 1 or more then 2 occurence of username.

select   x.username, x.item, y.username, y.item
from
(select id, username, item, FLOOR(1 + (RAND()) * (SELECT MAX(id)  FROM tst)) seq
  from tst) AS x
LEFT JOIN (select id, username, item FROM tst) AS y on x.username <> y.username
 order by x.seq
limit 1 ;

 

by: KupsiPosted on 2009-04-27 at 06:34:23ID: 24241461

Sorry, but I didn't get this to work.

 

by: theGhost_k8Posted on 2009-04-27 at 07:35:50ID: 24242132

20120131-EE-VQP-002

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