iOS-防止向SQLite数据库中插入重复数据记录：

原则：先检测该数据库的指定表中，是否已经存在我们要插入的这条数据记录，若已经存在，则不插入这条数据记录(即忽略此次插入操作)，若尚不存在，才插入这条数据记录(即才执行此次插入操作)

我们这里使用的是FMDB框架

FMDatabase *collectionBookDB = [FavoriteBooksDataBase favoriteBooksDataBase];

NSString *sqlObjectiveString = [NSString stringWithFormat:@"INSERT INTO t_favoriteBooks (bookName, author, publisher, publishmentDate, briefIntroduction, bookImageURL, bookIdentifier) SELECT ‘%@‘,‘%@‘,‘%@‘,‘%@‘,‘%@‘,‘%@‘, %d WHERE NOT EXISTS (SELECT * FROM t_favoriteBooks WHERE bookIdentifier=%d)", book.bookName, book.author, book.publisher, book.publishmentDate, book.briefIntroduction, book.bookImageURL, book.bookIdentifier, book.bookIdentifier];

BOOL collectionBookResult = [collectionBookDB executeUpdate:sqlObjectiveString];