Question

我正在尝试从数据库中删除创建行。但它没有这样做我有特定日期的内容在我的表中重复，所以我想删除特定日期的条目，并在每次建立连接时添加它们

我的代码是：

static sqlite3 *database = nil;
static sqlite3_stmt *deleteStmt = nil;

- (NSString *)dataFilePath {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(
                                                         NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:@"person.sqlite3"];
}


    NSDate *today = [NSDate date];
    NSLog(@"%@", today);
    NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
    [dateFormat setDateFormat:@"MM/dd/yy"];

    if (sqlite3_open([[self dataFilePath] UTF8String], &database)
        != SQLITE_OK)
    {
        sqlite3_close(database);
        NSAssert(0, @"Failed to open database");
    }


    NSString * dateString = [dateFormat stringFromDate:today];
    if(deleteStmt == nil)
    {
        const char *sql = "delete from SHOPPER where DATE = ?";
        if(sqlite3_prepare_v2(database, sql, -1, &deleteStmt, NULL) != SQLITE_OK)
            NSAssert1(0, @"Error while creating delete statement. '%s'", sqlite3_errmsg(database));
    }

    //When binding parameters, index starts from 1 and not zero.
    sqlite3_bind_text(deleteStmt, 3, [dateString UTF8String],-1, NULL);

    if (SQLITE_DONE != sqlite3_step(deleteStmt))
        NSAssert1(0, @"Error while deleting. '%s'", sqlite3_errmsg(database));

    sqlite3_reset(deleteStmt);

    sqlite3_close(database);

Answer 1

sqlite3_bind_text的第二个参数应为1，而不是3。它意味着指数'？'准备好的陈述中的字符，和因为只有一个'？'在您的删除语句中，它必须是1.

//When binding parameters, index starts from 1 and not zero.
sqlite3_bind_text(deleteStmt, 1, [dateString UTF8String], -1, NULL);

那么，为什么你将deleteStmt声明为static，并且只创建一次？我认为它应该是为开放数据库创建的，因为你打开了并且每次关闭数据库，你应该创建（并完成，而不是重置）每次都是deleteStmt。

从sqlite3数据库中删除某些行

1 个答案: