Réponses:
Tu peux le faire:
UPDATE table_name SET column=lower(column)
Reportez-vous à www.postgresql.org/docs/9.1/static/functions-string.html
HINT: No function matches the given name and argument types. You might need to add explicit type casts.
en essayant ceci.
UPDATE table_name SET column = LOWER(column) WHERE column != LOWER(column);
suffira.