• https://stackoverflow.com/questions/13804132/firebird-default-character-set
• https://stackoverflow.com/questions/32249389/convert-character-set-from-iso8859-1-to-utf8

• PDF : Character Sets and Unicode in Firebird (2011)

SELECT rdb$character_set_name FROM rdb$database;

Passage d'un champ en ISO8859_1 :

ALTER TABLE nom_de_la_table ALTER nom_du_champ TYPE VARCHAR(255) CHARACTER SET ISO8859_1;