c++ mysql connector check resultset is empty

Question

im using the MySQL Connector C++ library and want to check if a query is empty. Ive trief it like this:

  res = stmt->executeQuery("select max(date) from tab");
   if(res->next() == false )
     printf("empty! =? %s\n",  res->getString(1).c_str() );

this wont work. The table is empty and the if statement is always true.

Answer 1

Your query returns without HAVING clause a row, as is usual by using aggregate functions:

Use

SELECT MAX(date) FROM tab HAVING MAX(date) IS NOT NULL;

instead.

Demo