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Thread: Combining validation into main query

Combining validation into main query

From
Robert James
Date:
Typically, my web application does some initial validation, then, if
it passes, does the actual query.  For both performance and
simplicity, I'd like to combine these all into one trip to Postgres.
Ideally, I'd like to do this in SQL.  If that's not possible, I could
use PL/pgsql, though I'm not adept at it.

Example #1:
qry = "SELECT 1 FROM users WHERE username = ? AND PASSWORD = ?"
if qry.count > 0
    qry = "SELECT ..."

Example #2:
qry = "SELECT 1 FROM users WHERE username = ? AND PASSWORD = ?"
if qry.count > 0
  qry = "SELECT product WHERE ..."
  if qry.count > 0
     qry = "UPDATE product SET..."

How can I combine these into one Postgres call? I'd like it to look
something like:

GET_PRODUCTS(username, password) -- Returns products, or -1 if
username bad, -2 if password is bad

UPDATE_PRODUCTS(username, password, productid, newval) -- Updates
product, Returns 0 if good, -1 if username bad, -2 if password bad, -3
if productid bad

Re: Combining validation into main query

From
Serge Fonville
Date:
If you use EXISTS in the WHERE clause, you should come closer to what you want realised.
For further help it would make it easier if you shared the whole queries and perhaps a more detailed description of the goal you are trying to accomplish.

HTH

Kind regards/met vriendelijke groet,

Serge Fonville

http://www.sergefonville.nl

Convince Microsoft!
They need to add TRUNCATE PARTITION in SQL Server


2013/1/13 Robert James <srobertjames@gmail.com>
Typically, my web application does some initial validation, then, if
it passes, does the actual query.  For both performance and
simplicity, I'd like to combine these all into one trip to Postgres.
Ideally, I'd like to do this in SQL.  If that's not possible, I could
use PL/pgsql, though I'm not adept at it.

Example #1:
qry = "SELECT 1 FROM users WHERE username = ? AND PASSWORD = ?"
if qry.count > 0
    qry = "SELECT ..."

Example #2:
qry = "SELECT 1 FROM users WHERE username = ? AND PASSWORD = ?"
if qry.count > 0
  qry = "SELECT product WHERE ..."
  if qry.count > 0
     qry = "UPDATE product SET..."

How can I combine these into one Postgres call? I'd like it to look
something like:

GET_PRODUCTS(username, password) -- Returns products, or -1 if
username bad, -2 if password is bad

UPDATE_PRODUCTS(username, password, productid, newval) -- Updates
product, Returns 0 if good, -1 if username bad, -2 if password bad, -3
if productid bad


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Re: Combining validation into main query

From
Adrian Klaver
Date:
On 01/12/2013 04:58 PM, Robert James wrote:
> Typically, my web application does some initial validation, then, if
> it passes, does the actual query.  For both performance and
> simplicity, I'd like to combine these all into one trip to Postgres.
> Ideally, I'd like to do this in SQL.  If that's not possible, I could
> use PL/pgsql, though I'm not adept at it.
>
> Example #1:
> qry = "SELECT 1 FROM users WHERE username = ? AND PASSWORD = ?"
> if qry.count > 0
>      qry = "SELECT ..."
>
> Example #2:
> qry = "SELECT 1 FROM users WHERE username = ? AND PASSWORD = ?"
> if qry.count > 0
>    qry = "SELECT product WHERE ..."
>    if qry.count > 0
>       qry = "UPDATE product SET..."
>
> How can I combine these into one Postgres call? I'd like it to look
> something like:
>
> GET_PRODUCTS(username, password) -- Returns products, or -1 if
> username bad, -2 if password is bad
>
> UPDATE_PRODUCTS(username, password, productid, newval) -- Updates
> product, Returns 0 if good, -1 if username bad, -2 if password bad, -3
> if productid bad

So where are you running the above functions?
I would say you are going to end up using some procedural language to do
what you want. PL/pgsql is not that difficult to learn. If you end up
creating the functions on the server using plpgsql then you get your
simple query:

select get_products(username, password);

>
>


--
Adrian Klaver
adrian.klaver@gmail.com