My present understanding of placeholders is that they inform the database as to the form or pattern of subsequent queries, essentially providing structure to those queries which are yet to come.

I think perhaps I see where the misconception is here. What you are describing is query preparation and while that can be done for a single, isolated query it may not be necessary. However, placeholders are also used to safely interpolate data into the content of the current query. So you can use placeholders in a single query without performing explicit preparation. eg.

my $rows = $dbh->selectall_arrayref ('SELECT foo FROM bar WHERE quux =
+ ?', undef, $unsafe_input);

[download]

Always use placeholders. Always.

🦛

In reply to Re^7: Best practices for closing database connections? by hippo
in thread Best practices for closing database connections? by Polyglot

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