how to show a variable in MESSAGE_TEXT in signal query in c-CodePudding

I am using Signal query to catch errors in my c programming: in the program user has to enter a database name and i check the database if it does not exists I have to return proper error message:

std::string database_name;
std::cin<<database_name;
if(!exists(database_name)){
  query="SIGNAL SQLSTATE '42000' SET MYSQL_ERRNO='1049', MESSAGE_TEXT = 'Unknown database';";
}

how can I print the database_name variable after Unknown database?

CodePudding user response：

You can format the string using

query = std::format( "... MESSAGE_TEXT = 'Unknown database {}'", database_name );

This will replace {} with the first string argument (database_name)

Or you could just append the variable into it directly, like

query = "... MESSAGE_TEXT = 'Unknown database "   database_name   "'";