pl/sql PLS-00201 identifier must be declared - oracle

Question

Newbie to PL/SQL. I have several questions, so here's an example of what I'm trying to do.
CREATE OR REPLACE PROCEDURE "my_procedure" (
"my_inparam1" IN VARCHAR2,
"my_inparam2" IN VARCHAR2,
"my_output" OUT SYS_REFCURSOR)
AS
sql_text VARCHAR2 (10000);
BEGIN
sql_text :=
'select something
from my_table
where 1 = 1';
IF '&my_inparam1' <> 'foo'
THEN
sql_text := sql_text || ' and something = 0';
END IF;
IF '&my_inparam1' = 'foo' and '&my_inparam2' = 'bar'
THEN
sql_text := sql_text || ' and somethingelse = 1';
ELSIF '&my_inparam1' = 'foo' AND '&my_inparam2' = 'baz'
THEN
sql_text := sql_text || ' and somethingelse = 0';
END IF;
OPEN my_output FOR sql_text; --ERROR PLS-00201 Identifier 'MY_OUTPUT' must be declared
END;
So obviously I'm trying to return a query result, optionally filtered by whatever parameters I pass in. I'm at a loss as to why the offending line returns an error - in an earlier iteration, I was able to return results, but now, mysteriously, it's stopped working.
1) Is there a better way to approach this?
2) Do I have to reference the input params with the '&my_inparam' syntax?
3) If I do approach this by creating the sql text first and then opening the ref cursor, is there a shortcut for concatening the strings, like
sql_text &= ' and another_condition = 1'
?

Answer 1

In reverse order... no, there is no shorthand for concatenation like &=. You could use the concat() function instead, but the || method is more common, and more convenient especially if you're sticking more than two things together - nested concat() calls aren't as easy to follow. I'd stick with what you're doing.
Secondly, no, you're confusing SQL*Plus substitution variables with PL/SQL variables. Your references to '&my_inparam1' should be my_inparam1, etc; no ampersand and no quotes.
Except for some reason you've decided to make life difficult for yourself and use case-sentisive procedure and variable names, so you have to refer to "my_inparam1", in double quotes, everywhere.
That's why you're getting the message PLS-00201 Identifier 'MY_OUTPUT' must be declared. You didn't quote my_output so by default it's looking for a case-insensitive variable called MY_OUTPUT, which does not exist. It would work if you did this instead:
OPEN "my_output" FOR sql_text;
Unless you have a really really good reason, really don't do that.
CREATE OR REPLACE PROCEDURE my_procedure (
my_inparam1 IN VARCHAR2,
my_inparam2 IN VARCHAR2,
my_output OUT SYS_REFCURSOR)
AS
sql_text VARCHAR2 (10000);
BEGIN
sql_text :=
'select something
from my_table
where 1 = 1';
IF my_inparam1 <> 'foo'
THEN
sql_text := sql_text || ' and something = 0';
END IF;
...
OPEN my_output FOR sql_text;
END;
For more information, refer to the naming rules:
Every database object has a name. In a SQL statement, you represent
the name of an object with a quoted identifier or a nonquoted
identifier.
A quoted identifier begins and ends with double quotation marks (").
If you name a schema object using a quoted identifier, then you must
use the double quotation marks whenever you refer to that object.
A nonquoted identifier is not surrounded by any punctuation.
And more importantly:
Note:
Oracle does not recommend using quoted identifiers for database object names. These quoted identifiers are accepted by
SQL*Plus, but they may not be valid when using other tools that manage
database objects.
You quoted procedure name falls into this category; so do the quoted variable names. They're all identifiers and the same advice applies.