为了多线程操作数据库安全，FMDB使用了FMDatabaseQueue，使用FMDatabaseQueue很简单，首先用一个数据库文件地址来初使化FMDatabaseQueue，然后就可以将一个闭包(block)传入inDatabase方法中。 在闭包中操作数据库，而不直接参与FMDatabase的管理。

NSString *filePath=[[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"fmdb.sqlite"];
//创建数据库
self.db=[FMDatabase databaseWithPath:filePath];
//打开数据库
if ([self.db open]) {
    NSLog(@"打开数据库成功");
    //创建表格，除了select外，所有的操作都是更新
    BOOL createTableResult=[self.db executeUpdate:@"CREATE TABLE IF NOT EXISTS t_student (id integer PRIMARY KEY AUTOINCREMENT,name text,age integer)"];
    if (createTableResult) {
        NSLog(@"创建表成功");
    }else{
        NSLog(@"创建表失败");
    }
}else{
    NSLog(@"打开数据库失败");
}
}

- (IBAction)insert:(id)sender {
    for (int index=0; index<50; index++) {
        NSString *s_name=[NSString stringWithFormat:@"Andy%d",arc4random()%100];
        NSNumber *s_age=@(arc4random()%100);
        [self.db executeUpdate:@"INSERT INTO t_student(name,age) VALUES(?,?)",s_name,s_age];
    }
    }
    
    - (IBAction)delete:(id)sender {
        [self.db executeUpdate:@"DELETE FROM t_student WHERE id=?",@1];
        }
        
        - (IBAction)update:(id)sender {
            [self.db executeUpdate:@"UPDATE t_student SET name='Jack' WHERE id=?",@2];
            }
            
            - (IBAction)select:(id)sender {
                //获取结果集，返回参数就是查询结果
                FMResultSet *rs=[self.db executeQuery:@"SELECT * FROM t_student WHERE age>?",@50];
                while ([rs next]) {
                    int ID=[rs intForColumn:@"id"];
                    NSString *NAME=[rs stringForColumn:@"name"];
                    int AGE=[rs intForColumn:@"age"];
                    NSLog(@"%d %@ %d",ID,NAME,AGE);
                }

使用FMDatabaseQueue保证线程安全

NSString *filePath=[[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"fmdb.sqlite"];
//创建数据库，并加入到队列中，此时已经默认打开了数据库，无须手动打开，只需要从队列中去除数据库即可
self.queue=[FMDatabaseQueue databaseQueueWithPath:filePath];
//取出数据库，这里的db就是数据库，在数据库中创建表
[self.queue inDatabase:^(FMDatabase *db) {
//创建表
BOOL createTableResult=[db executeUpdate:@"CREATE TABLE IF NOT EXISTS t_student (id integer PRIMARY KEY AUTOINCREMENT,name text,age integer)"];
if (createTableResult) {
NSLog(@"创建表成功");
}else{
NSLog(@"创建表失败");
}
}];
}

- (IBAction)insert:(id)sender {
    [self.queue inDatabase:^(FMDatabase *db) {
        for (int index=0; index<50; index++) {
        NSString *s_name=[NSString stringWithFormat:@"Andy%d",arc4random()%100];
        NSNumber *s_age=@(arc4random()%100);
        [db executeUpdate:@"INSERT INTO t_student(name,age) VALUES(?,?)",s_name,s_age];
        }
        }];
    }
    
    - (IBAction)delete:(id)sender {
        [self.queue inDatabase:^(FMDatabase *db) {
            [db executeUpdate:@"DELETE FROM t_student WHERE id=?",@1];
            }];
        }
        
        - (IBAction)update:(id)sender {
            [self.queue inDatabase:^(FMDatabase *db) {
                [db executeUpdate:@"UPDATE t_student SET name='Jack' WHERE id=?",@2];
                }];
            }
            
            - (IBAction)select:(id)sender {
                [self.queue inDatabase:^(FMDatabase *db) {
                    //获取结果集，返回参数就是查询结果
                    FMResultSet *rs=[db executeQuery:@"SELECT * FROM t_student WHERE age>?",@50];
                    while ([rs next]) {
                    int ID=[rs intForColumn:@"id"];
                    NSString *NAME=[rs stringForColumn:@"name"];
                    int AGE=[rs intForColumn:@"age"];
                    NSLog(@"%d %@ %d",ID,NAME,AGE);
                    }
                    }];}

批处理回滚
__block BOOL result = YES；
[self.fmdbQueue inTransaction:^(FMDatabase db, BOOLrollback) {
NSDate *date = [NSDate date];
long long time = (long long)[date timeIntervalSince1970];
NSString *querySql = [NSString stringWithFormat:SQL_INSERT_FRIEND,aFriend.nubeNumber, aFriend.name, time];
LogWriterD(@"保存好友:%@",querySql);
result = result && [db executeUpdate:querySql];
if (!result) {
LogWriterE(@"保存好友失败，回滚保存操作");
*rollback = YES;
}}];