It seems like the wbs referencing is in the table planningelement.

Exemple :

mysql> select id,idProject,refId,refName,wbs,wbsSortable from planningelement order by wbsSortable;
+-----+-----------+-------+----------------------------------------------------------------+-------------+-------------------------+
| id  | idProject | refId | refName                                                        | wbs         | wbsSortable             |
+-----+-----------+-------+----------------------------------------------------------------+-------------+-------------------------+
|   2 |         2 |     2 | jordanpierrefabien                                             | 2           | 002                     |
|  11 |         2 |     7 | Analyse                                                        | 2.1         | 002.001                 |
|  10 |         2 |     6 | Analyse Fonctionnelle                                          | 2.1.1       | 002.001.001             |
|  13 |         2 |     9 | Validation de la solution                                      | 2.2         | 002.002                 |
|  23 |         2 |    19 | Recherche de solutions alternatives                            | 2.2.1       | 002.002.001             |
|  24 |         2 |    20 | Réception des documentations                                  | 2.2.2       | 002.002.002             |
|  25 |         2 |    21 | Validation du CDCT                                             | 2.2.3       | 002.002.003             |
|  12 |         2 |     8 | Modélisation                                                  | 2.3         | 002.003                 |
|  18 |         2 |    14 | Planification de projet                                        | 2.3.1       | 002.003.001             |
|  19 |         2 |    15 | Analyse des risques du projet                                  | 2.3.2       | 002.003.002             |
|  20 |         2 |    16 | Plan d'Assurance Qualité                                      | 2.3.3       | 002.003.003             |
|  21 |         2 |    17 | Plan de recette                                                | 2.3.4       | 002.003.004             |

Can i simply do an update of each record to solve my problem ?

No, never update direcly the database.
You may get unexpected result.

To force recalculation of WBS, just reorder the level.
To do this, in the planning view, create new projet "Draft".
It will get WBS 3.
Then drag&drop Draft to move it on first place.
It will get WBS 1.
Move "Draft" back to last position.
You main project will get WBS 1.
You can now deleted project "Draft"
It seems long, but it's easier to do than to descripbe what to do 😉

It works !
And you're right, it's better like this ^^

Great thanks 😉