====== Mysql ======


A tester en alternative de phpmyadmin => http://www.chive-project.com/

===== Tuto =====

  * http://www.mysqltutorial.org/


===== Cas d'une table de config avec une date =====

^ id      ^ user_id       ^ date          ^ name ^
| 1  | 1 | 2020-03-10 | toto |
| 2  | 1 | 2020-03-20 | super toto |
| 3  | 2 | 2020-01-01 | tata |

je veux les derniers nom des utilisateurs

<code sql>
select user_id, name
from users t1
WHERE EXISTS(SELECT 1
         FROM users t2
         WHERE t2.user_id = t1.user_id
         GROUP BY t2.user_id
         HAVING t1.date= MAX(t2.date))
</code>

^ user_id ^ name ^
| 1 | super toto |
| 2 | tata |

Par contre, si vous avez des date dans le futur, il faudra utiliser cette requête
<code sql>
select user_id, name
from users t1
WHERE EXISTS(SELECT 1
         FROM users t2
         WHERE t2.user_id = t1.user_id and t2.date<=now()
         GROUP BY t2.user_id
         HAVING t1.date= MAX(t2.date))
</code>


Variantes de la 1ère requête qui semble plus rapide
<code sql>
select t1.user_id,t1.name
from users as t1, 
(
  select user_id, MAX(date) as date
  from users
  group by user_id
) as t2
where
t1.user_id=t2.user_id and t1.date=t2.date
</code>