Re: named placeholders in DBI

[vladb]

in reply to named placeholders in DBI

This is of course true unless you are dealing with an automated process of building your queries from predefined perl structures. This would especially apply to building insert queries where data to be inserted is stored in a convenient perl hash (with keys being the fields and values being the corresponding field values :).

For example,

# a new record to be inserted
my %user_rec = (
                first_name => 'Foo',
                last_name => 'Bar',
                phone => '12345678',
                address => '123 Foo St',
                );

##
## . . . some code here . . .
##

# possibly somewhere in an add_db_user() sub
# ...
my @fields = keys %user_rec;
my @values = @user_rec{@fields};
my $placeholders = join(",", ("?") x scalar @fields);

my $sql = sprintf(qq~
                INSERT INTO user(%s) VALUES(%s)
                ~, join(",", @fields), $placeholders);

my $sth = $dbh->prepare($sql);
$sth->execute(@values);

In this specific example the query would be:

INSERT INTO user(first_name,address,last_name,phone) VALUES(?,?,?,?)

Introducing placeholders here may not be as useful or productive as say in a case where you build your SQL query 'manually'. ;)

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[simonm]

This functionality is also available pre-rolled in DBIx::SQLEngine:

my ($sql, @params) = DBIx::SQLEngine->sql_insert( 
                       table => 'users', values => \%user_rec );

There's also a dbh wrapper method that allows you to prepare and execute the query in one go:

my $sqldbh = DBIx::SQLEngine->new( ... ); # same args as DBI->connect
...
$sqldbh->do_insert( table => 'users', values => \%user_rec );