Collectives™ on Stack Overflow

Find centralized, trusted content and collaborate around the technologies you use most.

Teams

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

I am stuck in a problem and really hope you can help me. I like to convert a MySQL DATETIME field into a C++ std::time_t variable. My database looks like this:

CREATE TABLE data(
    id              INTEGER       AUTO_INCREMENT UNIQUE,
    path            VARCHAR(1000),
    acquisitionDate DATETIME
And I am trying to  save the value from acquisitionDate into a c++ variable of type std::time_t.
After some web searching I learned that I have to use UNIX_TIMESTAMP in my MySQL statement. However, I did not understand how to actual use it. I can generate a query and receive a sql::ResultSet:
std::unique_ptr<sql::Statement> stmt(mConnection->createStatement());
std::string query="SELECT id, path, UNIX_TIMESTAMP(acquisitionDate) FROM data WHERE id = 1";
std::unique_ptr<sql::ResultSet> res(stmt->executeQuery(query));
But I don't understand how I can get the actual field value into a std::time_t variable
if(res->next())
    std::time_t acquisitionDate =  res->getInt("acquisitionDate");
    std::time_t acquisitionDate =  res->???
Somehow my brain does not get this last step. Please help me.
Thank you very much!
I also understood that it is possible to access the fields output by:
std::time_t acquisitionDate =  res->getInt("UNIX_TIMESTAMP(acquisitionDate)");
Or the SQL statement could rename the field:
SELECT UNIX_TIMESTAMP(acquisitionDate) AS foo FROM data WHERE id = 1
and then 
std::time_t acquisitionDate =  res->getInt("foo");
However, casting should also be a good idea (after you have the correct field name):
std::time_t acquisitionDate =  static_cast<std::time_t>(res->getInt("foo"));
                You can also use an alias UNIX_TIMESTAMP(acquisitionDate) AS acquisitionDate or get the int by index res->getInt(2).
– Minding
                Nov 15, 2018 at 19:40
                Thanks a lot for your answer. Casting is a good and quite easy idea. However, I figured out that my problem was understanding how to access the returned field. See my answer to this question
– Michael
                Jul 7, 2016 at 11:34
        
Thanks for contributing an answer to Stack Overflow!
Please be sure to answer the question. Provide details and share your research!
But avoid …
Asking for help, clarification, or responding to other answers.
Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.