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.
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
