Programming the Perl DBI

Common Attributes

Common attributes are those that can be queried and set within both database and statement handles. This section discusses some of the most commonly used attributes, including:

PrintError

The PrintError attribute, when enabled, will cause the DBI to issue a warning when a DBI method returns with an error status. This functionality is extremely useful for rapid debugging of your programs, as you may not have written explicit return value checking code after every DBI statement.

The printed error string lists the class of the database driver through which the DBI method was dispatched, the method that caused the error to occur, and the value of $DBI::errstr. The following message was generated when the prepare() method did not successfully execute against an Oracle7 database using the DBD::Oracle driver:

DBD::Oracle::db prepare failed: ORA-00904: 
   invalid column name (DBD: error possibly near <*> indicator at char 8 in '
           SELECT <*>nname, location, mapref
           FROM megaliths
     ') at /opt/WWW/apache/cgi-bin/megalith/megadump line 79.

PrintError uses the standard Perl function called warn() to render the error message. Therefore, you could use a $SIG{_ _WARN_ _} error handler or an error handling module such as CGI::ErrorWrap to re-route the error messages from PrintError.

This attribute is enabled by default.

RaiseError

The RaiseError attribute is similar in style to its PrintError cousin, but differs slightly in operation. Whereas PrintError simply displayed a message when ...