--------------
SELECT cli.nom, art.nom
       FROM  cli,art,cmd
       WHERE cmd.nc=4 AND cmd.ncl=cli.nc AND art.na=cmd.nar
--------------

+--------+-------------+
| nom    | nom         |
+--------+-------------+
| DUPONT | VELO ADULTE |
+--------+-------------+
1 row in set (0.00 sec)

--------------
SELECT " Commande "    , cmd.nc ,
       " Client   "    , cli.nom  ,
       " Article  "    , art.nom ,
       " Fournisseur " , four.nom
       FROM  cmd,cli,art,four
       WHERE cmd.ncl=cli.nc AND cmd.nar=art.na AND art.four=four.nf
       ORDER BY cmd.nc
--------------

+------------+----+------------+----------+------------+---------------+---------------+------------------+
| Commande   | nc | Client     | nom      | Article    | nom           | Fournisseur   | nom              |
+------------+----+------------+----------+------------+---------------+---------------+------------------+
|  Commande  |  1 |  Client    | BOND     |  Article   | MONTRE FEMME  |  Fournisseur  | Gifts Inc.       |
|  Commande  |  2 |  Client    | GELIF    |  Article   | HALOGENE LUXE |  Fournisseur  | Cadeaux S.A.R.L. |
|  Commande  |  3 |  Client    | BOUTRISE |  Article   | TASSE DECO2   |  Fournisseur  | Gifts Inc.       |
|  Commande  |  4 |  Client    | DUPONT   |  Article   | VELO ADULTE   |  Fournisseur  | Jouets S.A.      |
|  Commande  |  5 |  Client    | BOND     |  Article   | MONTRE FEMME  |  Fournisseur  | Gifts Inc.       |
|  Commande  |  6 |  Client    | BOND     |  Article   | MONTRE HOMME  |  Fournisseur  | Gifts Inc.       |
+------------+----+------------+----------+------------+---------------+---------------+------------------+
6 rows in set (0.00 sec)

--------------
SELECT cli.nom,  COUNT(cli.nom) AS ndc
       FROM  cli,cmd
       WHERE cmd.ncl=cli.nc
       GROUP BY cli.nom
       ORDER BY ndc DESC , cli.nom
--------------

+----------+-----+
| nom      | ndc |
+----------+-----+
| BOND     |   3 |
| BOUTRISE |   1 |
| DUPONT   |   1 |
| GELIF    |   1 |
+----------+-----+
4 rows in set (0.00 sec)

--------------
SELECT DISTINCT cli.nom
       FROM cli LEFT JOIN cmd
       ON   cli.nc=cmd.ncl
       WHERE cmd.ncl IS NULL
       ORDER BY cli.nom
--------------

+------------+
| nom        |
+------------+
| ALISSANNE  |
| DE MARNETS |
| FROGARIN   |
| LUCAS      |
| MAUPINTON  |
| ZELAZNOHYG |
+------------+
6 rows in set (0.00 sec)

--------------
SELECT art.nom AS nom_article, IF(ISNULL(SUM(cmd.qte)),0,SUM(cmd.qte)) AS nbcmd
       FROM art LEFT JOIN cmd  ON cmd.nar=art.na
       GROUP BY art.nom
       ORDER BY nbcmd DESC , art.nom
--------------

+--------------------+-------+
| nom_article        | nbcmd |
+--------------------+-------+
| MONTRE FEMME       |     5 |
| TASSE DECO2        |     3 |
| HALOGENE LUXE      |     1 |
| MONTRE HOMME       |     1 |
| VELO ADULTE        |     1 |
| BALLON OVALE       |     0 |
| BALLON ROND        |     0 |
| COUVERTURE BLEUE   |     0 |
| COUVERTURE JAUNE   |     0 |
| COUVERTURE ROUGE   |     0 |
| HALOGENE           |     0 |
| HALOGENE MIXTE     |     0 |
| LAMPADAIRE         |     0 |
| MONTRE ENFANT      |     0 |
| TABOURET PLASTIQUE |     0 |
| TASSE DECO1        |     0 |
| TASSE DECO3        |     0 |
| TASSE DECO4        |     0 |
| VASE ROSE          |     0 |
| VELO ENFANT        |     0 |
+--------------------+-------+
20 rows in set (0.00 sec)

--------------
SELECT four.nom, COUNT(art.four) AS nbcmd
       FROM four LEFT JOIN cmd,art
       ON four.nf=art.four
       WHERE cmd.nar=art.na OR art.four IS NULL
       GROUP BY art.four
       ORDER BY nbcmd DESC
--------------

+------------------+-------+
| nom              | nbcmd |
+------------------+-------+
| Gifts Inc.       |     4 |
| Cadeaux S.A.R.L. |     1 |
| Jouets S.A.      |     1 |
| L3S              |     0 |
+------------------+-------+
4 rows in set (0.00 sec)

Bye