[PD] Question about SQL Placeholder Implementation

[Mike McGonagle]

On 12/21/07, Mathieu Bouchard <matju at artengine.ca> wrote:
>
> On Tue, 18 Dec 2007, Mike McGonagle wrote:
>
> > [query <srv_id> insert into mytable (id, name, token) values
> (?f,'?s','?s')]
> > In this example, the first placeholder would expect a Float, with the
> next
> > two expecting a Symbol (just think of this as a variation on the printf
> > string substitutions).
>
> It looks more like the types of [t] [pack] [unpack] [expr] etc.



Yes, they are PD types.


You don't really need to type your data. SQL is largely typeless: at least
> at the level of what you can put in one table cell, anything is a string.
> It becomes typed (but auto-cast) when put in the cell, but rebecomes
> untyped when taken out of the cell.



Yes, I know that these things can be stored in a typeless manner, but the
functions that bind the SQL statement with their placeholders can be of any
type, as there are functions for the various datatypes.

http://www.sqlite.org/c3ref/bind_blob.html

This link shows all the different functions used to bind the data to the
statement placeholders.

http://dev.mysql.com/doc/refman/5.0/en/c-api-prepared-statement-datatypes.html

And if you look at how MySQL does this, while they only provide a single
bind function, it does have the datatypes for the data in a structure that
gets passed into the bind function.

Also, from looking at libdbi, it appears that they don't even bother with
placeholders at all.

This is not an issue of how the user sees these things, it is how the C code
interfaces with the database.

So, just how do we do this in a consistent manner when all the different
interfaces don't support these things, AND if they do, they do them
differently.

> but considering that the databases need to know the specific data types
> > for each placeholder,
>
> heh? do they?



SQLite does. MySQL appears to as well. And yes, it is possible to just force
everything to be a string/c-string and be done with it. SQLite actually
stores everything as a string anyway, despite the defined types in the
create statement.

Mike


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> | Mathieu Bouchard - tél:+1.514.383.3801, Montréal QC Canada




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