使用连接语句更新数据库时FMDB语法错误

Question

我试图更新以下数据库中的列;

create table movies(id integer primary key AUTOINCREMENT, imdb_id varchar(60) UNIQUE, title varchar(100), plot varchar(1000),poster varchar(1000),rating real, predicted_rating real, year integer, is_watched integer); 

create table genres(id integer primary key AUTOINCREMENT, genre varchar(60) UNIQUE); 

create table movie_genres(id integer primary key AUTOINCREMENT, genres_id integer , movies_id integer, FOREIGN KEY(movies_id) REFERENCES movies(id),FOREIGN KEY(genres_id) REFERENCES genres(id)); 

我的代码在IOS

[_writeQueue addOperationWithBlock:^{ 
      [_writeQueueLock lock]; 
      [_queue inDatabase:^(FMDatabase *database) { 
       BOOL success = [database executeUpdate:@"UPDATE movies SET m.predicted_rating = m.predicted_rating + 0.05 from movies m left join movie_genres g on m.id = g.movies_id where g.genres_id = ? ;",[NSNumber numberWithInt:genreId], nil]; 
       if (success==YES) { 
        NSLog(@"prediction calculated"); 
       } 
       else{ 
        NSLog(@"prediction failed"); 
       } 
      }]; 
      [_writeQueueLock unlock]; 
     }]; 

错误：

prediction failed 
DB Error: 1 "near ".": syntax error" 

缺少什么我在这里？

Answer 1

SQLite不允许直接在UPDATE语句中连接。

你必须使用一个子查询：

UPDATE movies 
SET predicted_rating = predicted_rating + 0.5 
WHERE id IN (SELECT movies_id 
      FROM movie_genres 
      WHERE genres_id = ?)