Select distinct

From ClassDBI

Selecting Distinct Values

Problem:

You want the Class::DBI equivalent of "SELECT DISTINCT column FROM table;" For example, "SELECT DISTINCT address FROM photos WHERE projno=?"

Solution:

There isn't really an equivalent, as Class::DBI is about returning objects rather than values.

In this sort of case, people generally use Perl:

 my %seen;
 my @address = grep !$seen{$_}++, map $_->address,
     Photo->search(projno => $value);

But you can also merrily write your own method to do this:

 __PACKAGE__->set_sql(distinct_col_by_proj => <<);
     SELECT DISTINCT(%s)
     FROM   __TABLE__
     WHERE  projno = ?
 
 sub addresses_for_proj {
     my ($class, $projno) = @_;
     return $class->sql_distinct_col_by_proj('address')->select_col($projno); 
 }

Solution by Tony via list

Transcribed by Vince Veselosky