C++ 将修改后的 MySQL 时间戳存储为字符串 [英] C++ store a modified MySQL timestamp as string

问题描述

我目前正在尝试从 MySQL 数据库中获取 DATETIME 键值并将其保存为字符串.

I am currently trying to get a DATETIME key value from a MySQL database and save it as a string.

但是我不希望时间采用通常的 MySQL 格式 YYYY-MM-DD HH:MM:SS 而是采用这样的 12 小时格式:HH:MM:SS 上午/下午

However I dont want the time to be in the usual MySQL format YYYY-MM-DD HH:MM:SS but rather in a 12 hour format like this: HH:MM:SS AM/PM

我已经想出了如何使用以下方法将 MySQL 数据库中的时间格式转换"为我想要的格式:

I already figured out how to "convert" the time format in the MySQL database to my desired format by using this:

sql::ResultSet* time = database->Query("SELECT DATE_FORMAT(`lastLogin`, '%r') FROM `users` WHERE `user_id`='%i', id);

MySQL 命令有效，Query 返回正确的时间格式(我直接在 MySQL 中测试过).

the MySQL command is valid and the Query returns the right time format (I tested it directly in MySQL).

现在我想将结果存储在 char* 数组中，但由于某种原因，当我尝试将结果复制到数组时，他总是因 SQL 无效命令异常而崩溃.

Now I want to store the result in a char* array but for some reason he always crashes with a SQL Invalid Command Exception when I try to copy the result in to the array.

time->first();
char* lastLogin = new char[50];

//here are the variants of the commands I tried, every one crashed:
strcpy(lastLogin, time->getString("lastLogin").c_str());
strcpy(lastLogin, time->getString("DATE_FORMAT(`lastLogin`, '%r')").c_str());
strcpy(lastLogin, time->getString("DATE_FORMAT(lastLogin, '%r')").c_str());
strcpy(lastLogin, time->getString(0).c_str());

有人知道我做错了什么吗?或者这甚至可以用 MySQL Connector C++ 实现吗?

does anybody know what I am doing wrong? Or is this even possible with MySQL Connector C++?

推荐答案

尝试为 SQL 中的表达式命名，并给它一个别名:

Try naming the expression in your SQL, giving it an alias:

"SELECT DATE_FORMAT(`lastLogin`, '%r') as last_login_str FROM `users` WHERE `user_id`='%i'"

然后使用 "last_login_str" 来检索值.

Then use "last_login_str" to retrieve the value.

这篇关于C++ 将修改后的 MySQL 时间戳存储为字符串的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！