http://search.cpan.org/~timb/DBI/DBI.pm

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Placeholders and Bind Values

Some drivers support placeholders and bind values. Placeholders, also called parameter markers, are used to indicate values in a database statement that will be supplied later, before the prepared statement is executed. For example, an application might use the following to insert a row of data into the SALES table:

INSERT INTO sales (product_code, qty, price) VALUES (?, ?, ?)

or the following, to select the description for a product:

SELECT description FROM products WHERE product_code = ?

The ? characters are the placeholders. The association of actual values with placeholders is known as binding, and the values are referred to as bind values. Note that the ? is not enclosed in quotation marks, even when the placeholder represents a string.

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