Programming the Perl DBI

Name

bind_ param

Synopsis

$rc = $sth->bind_param($p_num, $bind_value) || die
$sth->errstr;
$rv = $sth->bind_param($p_num, $bind_value, \%attr)     || ...
$rv = $sth->bind_param($p_num, $bind_value, $bind_type) || ...

The bind_ param method can be used to bind a value with a placeholder embedded in the prepared statement. Placeholders are indicated with the question mark character (?). For example:

$dbh->{RaiseError} = 1;        # save having to check each method call
$sth = $dbh->prepare("SELECT name, age FROM people WHERE name LIKE ?");
$sth->bind_param(1, "John%");  # placeholders are numbered from 1
$sth->execute;
DBI::dump_results($sth);

Note that the ? is not enclosed in quotation marks, even when the placeholder represents a string. Some drivers also allow placeholders like : name and : n (e.g., :1, :2, and so on) in addition to ?, but their use is not portable. Undefined bind values or undef can be used to indicate null values.

Some drivers do not support placeholders.

With most drivers, placeholders can’t be used for any element of a statement that would prevent the database server from validating the statement and creating a query execution plan for it. For example:

"SELECT name, age FROM ?"         # wrong (will probably fail)
"SELECT name, ?   FROM people"    # wrong (but may not 'fail')

Also, placeholders can only represent single scalar values. For example, the following statement won’t work as expected for more than one value:

"SELECT name, age FROM people WHERE name IN (?)"    # wrong

Datatypes for ...