MySQL Stored Procedure Programming

Executing Stored Programs with DBD::mysql

We can use the techniques we’ve discussed in the previous sections for executing stored programs, although there are some circumstances in which you will need to use some additional techniques—specifically, if you need to retrieve multiple result sets or retrieve the value of an output parameter.

To execute a simple, one-off stored procedure that returns no result sets, we can simply invoke it with the do() method of the database handle, as shown in Example 15-20.

Example 15-20. Executing a very simple stored procedure

my $sql = 'call simple_stored_proc(  )';

$dbh->do($sql)||die $DBI::errstr;

Stored procedures that return only a single result set can be treated in the same manner as simple SELECT statements. Example 15-21 shows a stored procedure that returns just one result set.

Example 15-21. Simple stored procedure with a result set

CREATE PROCEDURE department_list(  )
    SELECT  department_name,location from departments;

Example 15-22 shows how we would retrieve that result set in Perl. The approach is exactly the same as the one we would use for a SELECT statement or other SQL that returns a result set.

Example 15-22. Fetching a single result set from a stored procedure

    my $sth = $dbh->prepare('call department_list(  )') || die $DBI::errstr;
    $sth->execute || die $DBI::errstr;
    while ( my @row = $sth->fetchrow_array ) {
         print join("\t",@row),"\n";
    }
    $sth->finish;

Input parameters can be treated in the same way as placeholders in standard SQL. Input ...