Programming the Perl DBI

Name

execute

Synopsis

$rv = $sth->execute                || die $sth->errstr;
$rv = $sth->execute(@bind_values)  || die $sth->errstr;

Performs whatever processing is necessary to execute the prepared statement. An undef is returned if an error occurs. A successful execute always returns true regardless of the number of rows affected, even if it’s zero (see below). It is always important to check the return status of execute (and most other DBI methods) for errors.

For a non-SELECT statement, execute returns the number of rows affected, if known. If no rows were affected, then execute returns 0E0, which Perl will treat as 0 but will regard as true. Note that it is not an error for no rows to be affected by a statement. If the number of rows affected is not known, then execute returns -1.

For SELECT statements, execute simply “starts” the query within the database engine. Use one of the fetch methods to retrieve the data after calling execute. The execute method does not return the number of rows that will be returned by the query (because most databases can’t tell in advance), it simply returns a true value.

If any arguments are given, then execute will effectively call bind_ param for each value before executing the statement. Values bound in this way are usually treated as SQL_VARCHAR types unless the driver can determine the correct type (which is rare), or unless bind_ param (or bind_ param_inout) has already been used to specify the type.