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## 4. Running an Example Database

After completing the system installation we can now finally run a model application. Depending on the version of msql installed and the perl database interface used, we have to modify the sample programs in a few points.

First however, the file `index.html` residing in `/home/httpd/html/` must be modified to allow calling a sample database application. We can place our database (which we call `database.cgi` or `inventur.cgi` here despite its archive name `perl.lst.ck`) in `/home/httpd/html/test/`.

We add one line (of course, depending on your installation choices) similar to the following to `index.html`:

    <LI>Test the <A HREF="test/database.cgi">Database, DBI:DBD-mSQL style!</A>
    <LI>Test the <A HREF="test/inventur.cgi">Database, MsqlPerl style!</A>

Usually you should only pick one of these two choices but if you have both types of database interface installed you can leave both lines here as they are. You can then compare performance, etc.

## 4.1 Adapting the sample script for MsqlPerl

Our sample script has to be told to use the MsqlPerl interface. The modification takes place in several locations. First, near the beginning of the file, we change the `use` clause:

    #
    # use DBI;            # Generisches Datenbank-Interface
    use Msql;

Then, near line 27, the MsqlPerl syntax does not require the mentioning of a specific driver:

    # $dbh = DBI->connect($host, $database, '', $driver) ||
    $dbh = Msql->connect($host, $database) ||

Then, from line 33 onward throughout the whole script, we have to change all instances of `do` against `query`:

    # $dbh->do("SELECT * FROM hw") || db_init($dbh);
    $dbh->query("SELECT * FROM hw") || db_init($dbh);

Finally, in MsqlPerl speak, line 207 can be commented out:

    # $sth->execute || msg("SQL Error:", $sth->errstr);

In addition, it may become necessary to swap all `errstr` calls like the one in the preceding code fragment against `errmsg`. This is also version dependent.

After these modifications, the script should run smoothly.

## 4.2 Adapting the sample script for msql-2

The SQL syntax was redefined during the development of mslq-2. The original script will fail to execute the table initialization statements in lines 45 -- 58. The `primary key` modifier is no longer supported by msql-2, and should simply be skipped:

        $dbh->do(<<EOT) || die $dbh->errstr; # Neue Personen-Tabelle
            create table person (
    # We do not need the 'primary key' modifier anymore in msql-2!
    #           pn        int primary key,   # Personalnummer
                pn        int,               # Personalnummer
                name      char(80),          # Nachname, Vorname
                raum      int                # Raumnummer
            )
    EOT
        $dbh->do(<<EOT) || die $dbh->errstr; # Neue Hardware-Tabelle
            create table hw (
    # We do not need the 'primary key' modifier anymore in msql-2!
    #           asset int primary key,       # Inventurnummer
                asset int,                   # Inventurnummer
                name   char(80),             # Bezeichnung
                person int                   # Besitzer
            )
    EOT

Unfortunately, this specific script will then accept new entries with identical personnel numbers; the msql-1 modifier `primary key` intends to prevent exactly this behaviour. The msql-2 documentation shows how to use the `CREATE INDEX` clause to create unique entries.

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