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Editorial Team
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Asked: 2026-06-02T11:10:32+00:00

I would like get 3 random stamps, but each from different country. This query

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I would like get 3 random stamps, but each from different country. This query return random stamps, but could be from the same country. When I add GROUP BY country_id I will get 3 stamps of different countries, but only first stamps of each country.

SELECT `stamps`.`stamp_id`, `countries`.`country_name_cs` FROM `stamps`
LEFT JOIN `countries` ON countries.country_id = stamps.country_id
WHERE (stamps.stamp_enabled = 1) ORDER BY rand() ASC LIMIT 3

Any idea?

Query profile (#Ezequiel Muns solution)

starting              0.000232
Opening tables        0.000047
System lock           0.000013
Table lock            0.000635
optimizing            0.000036
statistics            0.000022
preparing             0.000023
Creating tmp table    0.000293
executing             0.000004
Copying to tmp table  0.060066
Sorting result        0.013835
Sending data          0.089164
removing tmp table    0.000632
Sending data          0.000026
init                  0.000048
optimizing            0.000014
statistics            0.000061
preparing             0.000028
Creating tmp table    0.000326
executing             0.000004
Copying to tmp table  0.353176
Sorting result        0.000158
Sending data          0.000038
end                   0.000005
removing tmp table    0.000018
end                   0.000006
query end             0.000004
freeing items         0.000575
removing tmp table    0.002363
closing tables        0.000023
logging slow query    0.000004
cleaning up           0.000009

id      select_type       table      type       possible_keys       key         key_len     ref           rows      Extra
1       PRIMARY       <derived2>     ALL        NULL                NULL        NULL        NULL          12679     Using temporary; Using filesort
1       PRIMARY       c              eq_ref     PRIMARY             PRIMARY     4           s.country_id  1      
2       DERIVED       stamps         ALL        NULL                NULL        NULL        NULL          12679     Using where; Using temporary; Using filesort
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1 Answer

  1. Editorial Team

    You can try the following query, this selects 3 random countries first, performs a join with a mixed stamp table, and then groups by country. Not efficient, but workable for smaller data sets.

     SELECT
    mixed_stamp.stamp_id,
    random.country_name_cs
 FROM
    (SELECT * FROM stamps ORDER BY RAND()) AS mixed_stamp
 LEFT JOIN (SELECT country_id FROM countries ORDER BY RAND() LIMIT 3) random ON (random.country_id = mixed_stamp.country_id)
 GROUP BY random.country_id
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