file_path is unique

database/init.sql

@@ -13,7 +13,7 @@ CREATE TABLE IF NOT EXISTS kara
   , category    INTEGER NOT NULL REFERENCES kara_category
   , song_type   INTEGER NOT NULL REFERENCES kara_type
   , language    TEXT    REFERENCES language
-  , file_path   TEXT    NOT NULL
+  , file_path   TEXT    NOT NULL UNIQUE
   , is_new      INTEGER NOT NULL
   , author_name TEXT
   , author_year INTEGER CHECK(author_year > 0)