Atomic and Batch Fetching

Atomic and batch fetching are two slightly more interesting ways of getting data out of your database. The two procedures are somewhat related to each other, in that they potentially make life a lot easier for you, but they do it in radically different ways.

Atomic Fetching

When you want to fetch only one row, atomic fetching allows you to compress the four-stage data fetching cycle (as described earlier) into a single method. The two methods you can use for atomic fetching are selectrow_array( ) and selectrow_arrayref( ) . They behave in a similar fashion to their row-oriented cousins, fetchrow_array( ) and fetchrow_arrayref( ), the major differences being that the two atomic methods do not require a prepared and executed statement handle to work, and, more importantly, that they will return only one row of data.

Because neither method requires a statement handle to be used, they are actually invoked via a database handle. For example, to select the name and type fields from any arbitrary row in our megaliths database, we can write the following code:

### Assuming a valid $dbh exists...
( $name, $mapref ) = 
    $dbh->selectrow_array( "SELECT name, mapref
                            FROM megaliths" );
print "Megalith $name is located at $mapref\n";

This is far more convenient than using the prepare() and execute() then the fetchrow_array( ) or fetchrow_arrayref( ) methods for single rows.

Finally, bind values can be supplied, which again helps with the reuse of database resources.