jeanluca,

If you read the DBI documentation under Placeholders and Bind Values you will find:

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')

If in doubt check out the DBI documentation, and the documentation for the driver you are using.

Hope this helps

Martin