Question

How to determine connection state of Perl DBI database handler(is connection opend)? Something like .NET SqlConnection.State == Open. May be something like

defined($dbh->do("some nop sql"))

but can’t find sql nop statement to use.

Answer 1

You can ask you database handle if it is connected by calling

$dbh->ping();

Some DB Drivers don’t implement ping but DBD::mysql does. An alternative is to run an empty select like select 1 for MySQL. I’m assuming MySQL since that is how your question is tagged. Other databases will have slightly different answers.