thank for your answer,

since the time of question (late november 2018)  as i had no solution else remove the accent from database which would have for consequence to change a lot in existing code (in Java,Scheme,Kawa and Haskell) i had used

Database.MySQL.Simple which worked 'out of the box' for accents.

i have checked the locale on both client and server and it is  the same:

LANG=en_US.UTF-8

client:

[mattei@asteroide Haskell]$ echo $LANG
en_US.UTF-8

server:

[root@moita ~]# echo $LANG
en_US.UTF-8

if i unset LANG it's worse all accent character display as ? or disappears:

*Main> main
2139
select `NumBD` from 'sidonie.Coordonn?es' where Nom = 'A    20'
*** Exception: SqlError {seState = "", seNativeError = 1064, seErrorMsg = "You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ''sidonie.Coordonnes' where Nom = 'A    20'' at line 1"}

but the database seems to use latin1 as show below:

MariaDB [sidonie]> SHOW FULL COLUMNS FROM Coordonnées;
+----------------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+
| Field          | Type        | Collation         | Null | Key | Default | Extra | Privileges                      | Comment |
+----------------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+
| N° Fiche       | int(11)     | NULL              | NO   | PRI | 0       |       | select,insert,update,references |         |
| Alpha 2000     | double      | NULL              | YES  |     | NULL    |       | select,insert,update,references |         |
| Delta 2000     | double      | NULL              | YES  |     | NULL    |       | select,insert,update,references |         |
| N° ADS         | varchar(50) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
| NomSidonie     | varchar(50) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
| mag1           | varchar(50) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
| mag2           | varchar(50) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
| N° BD          | varchar(50) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
| Spectre        | varchar(50) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
| N°Type         | float       | NULL              | YES  |     | NULL    |       | select,insert,update,references |         |
| N° HIP         | varchar(50) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
| Orb            | varchar(50) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
| Modif          | datetime    | NULL              | YES  |     | NULL    |       | select,insert,update,references |         |
| Date de saisie | datetime    | NULL              | YES  |     | NULL    |       | select,insert,update,references |         |
| Nom opérateur  | varchar(50) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
| Nom            | varchar(50) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
+----------------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+
16 rows in set (0.00 sec)

i still do not know woth HDBC where to put the options at the connection to set encoding in my code i had this:

do
    conn <- connectMySQL defaultMySQLConnectInfo {
                       mysqlHost     = "moita",
                       mysqlUser     = "mattei",
                       mysqlPassword = ""
                    }

i can not fin in doc an option for encoding

the solution to do :SET NAMES utf8;

i try this:

config  <- quickQuery' conn "SET NAMES utf8" []

but i get an error :

*Main> main
*** Exception: SqlError {seState = "", seNativeError = 2053, seErrorMsg = "Attempt to read a row while there is no result set associated with the statement"}

because SET return an empty result list,

do not know how to make it work....

Damien