Jawaban:
Kamu bisa melakukan ini:
UPDATE table_name SET column=lower(column)
Lihat 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.
saat mencoba ini.
UPDATE table_name SET column = LOWER(column) WHERE column != LOWER(column);
akan dilakukan.