根据时间删除sqlite3中数据

//根据时间删除

- (void)deleteDataWithTime:(NSString *)time at:(NSString *)tableName{

    //NSString *deleteSql = @"delete from LBBMesTable where Id =?";

    NSString *tab = [tableName stringByReplacingOccurrencesOfString:@".db" withString:@""];

    NSString *deleteSql = [NSString stringWithFormat:@"delete from %@ where time <?",tab];

   // NSData *messageData = [message dataUsingEncoding:NSUTF8StringEncoding];

    NSString *path = [NSHomeDirectory() stringByAppendingString:[NSString stringWithFormat:@"/Documents/%@",tableName]];

    _dataBase = [FMDatabase databaseWithPath:path];

    if([_dataBase open]){

        if (![_dataBase executeUpdate:deleteSql,time]) {

            NSLog(@"delete error:%@",_dataBase.lastErrorMessage);

        }

    }

    [_dataBase close];

}

这样可以直接删除哪个时间之前的数据,其中time是以字符串存储的,相当于比较字符串了,

//计算距离现在多少秒的时间,返回的是时间的完整字符串,如2014-01-04 06:06:06,如果传入的是负数,则是以前的时间

+(NSString *)timeStrSinceNow: (NSTimeInterval)timeInterval{

    NSDate* dat = [NSDate dateWithTimeIntervalSinceNow:timeInterval];//计算出这么多时间之前的一个时间

    NSDateFormatter *formatter=[[NSDateFormatter alloc] init];

    [formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

    NSString *pastTime = [formatter stringFromDate:dat];

    return pastTime;

}