[PD] [psql] object hand-holding

Mathieu Bouchard matju at artengine.ca
Sat Dec 8 06:51:18 CET 2007

On Fri, 7 Dec 2007, Hans-Christoph Steiner wrote:

> That is done by sending the [submit( message to the hot inlet.  Or do you 
> mean having multiple SQL calls separated by semi-colons?  If you wanted to 
> add semicolons, there would have to be a special message, I think we could 
> just reuse the "addsemi", "addcomma", "adddollar" messages from message 
> boxes.

The only SQL interface I'd really be happy to use (if I had to use SQL) is 
something using placeholders, sort of like [expr], but perhaps written in 
the usual SQL style:

[sql select * from candies where flavour=? and colour=?]

you wouldn't modify the statement any more than you modify an [expr] at 
runtime. this allows the statement to be precompiled by the server. you 
could still allow runtime change but perhaps it would get messy with 
multiple inlets, so let's assume for now that it is not supported.

in the above example, [sql] has two inlets, one for each question-mark. 
Sending a list in the hot inlet is also correct, and "set" and "bang" do 
as usual. Each value will be quoted automatically, with appropriate 
apostrophes and backslashes and stuff, so that the user never has to do 
it. (my biggest problem with PHP is the lack of this feature).

an alternate way to do it is to use the same syntax as [expr]. This allows 
a repeated value to not have to be repeated in the input to the object. 
However, this means that values are going to be typed, which is a bad 
match with SQL, which doesn't type values (it only types table cells 
themselves and casts everything automatically).

> As far as I know, the semi-colon at the end of the statement in SQL triggers 
> the execution of that statement

With this interface, there would be no semicolon at the end (or it would 
be optional and useless). The execution is done each time the hot inlet is 
activated (bang, float, symbol or list, but not others like set and 
whatever else if there's anything else).

> so I can't see an advantage to having multiple, semi-colon terminated 
> statements in a single message box.  Does it change how the SQL is 
> executed if they are submitted at the same time?

Multiple statements are compiled as one function to which you pass all 
arguments you want at once. This could be useful if you want to do both 
insert and select in one go. It may be a bit faster, or maybe not, but 
it's convenient.

[expr] supports semicolons and uses them for multiple outputs. For [sql], 
it might make only sense to have one outlet per query rather than by 
statement: that is, only SELECT and EXPLAIN and such would get an outlet, 
while INSERT and DELETE wouldn't, for example.

At this point, I can't think of a case where I'd like to modify a SQL 
statement at runtime. Somehow it's possible to find a use, but I think 
that for almost everything you don't.

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

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