ORA-01403 when referencing page item in PL/SQL - oracle

Question

I am building an Oracle ApEx page to show charts of data. The data are entered on to a table as inputs, but the actual calculated metric can be different depending on what KPI is being viewed (AVG(VALUE_1); SUM(VALUE_1)/SUM(VALUE_2); etc.); these calculations are stored on a separate table. Since I want everything to be dynamic for use interactions, I am using a source of PL/SQL Function Body returning SQL Query. Here is a simplified version
DECLARE
SQL_STMT VARCHAR2 (32767);
CALC_CLAUSE VARCHAR2 (4000);
BEGIN
SELECT CALCULATION
INTO CALC_CLAUSE
FROM KPI_TYPES
WHERE ID = 101;
--when the value itself is entered, the results display as intended
SQL_STMT := 'SELECT DATE, ' || CALC_CLAUSE || ' KPI_VALUE
FROM DATA_VALUES
WHERE TYPE_ID = :P_KPI
GROUP BY DATE';
RETURN SQL_STMT;
END;
As noted above, this functions as expected when the KPI's ID is manually entered, but I want this to be dynamic. I have a select list page item (P_KPI) for the user to choose the viewed KPI. Its value is actually set from a previous page with validation, so it should never be null.
When I update the CALC_CLAUSE condition:
WHERE ID = :P_KPI
I receive the following error:
ORA-01403: no data found
How can I reference this page item in the function?

Answer 1

Code you posted is invalid (wouldn't compile) and explanation you gave is wrong. Although it is a simplified version, I'd prefer if you posted accurate information.
You said that SQL statement is
SELECT DATE, '||CALC_CLAUSE||' KPI_VALUE
FROM DATA_VALUES ...
while CALC_CLAUSE looks like
WHERE ID = :P_KPI
so the whole query looks like
SELECT DATE, WHERE ID = :P_KPI KPI_VALUE
FROM DATA_VALUES ...
which just doesn't make sense. What is that CALC_CLAUSE, after all? Shouldn't it be AVG(VALUE_1) or something like that?
As of :P_KPI item whose value seems to be NULL: it doesn't matter that you see it on the screen - it should be in the session state. The simplest way to do that is to submit the page, so - did you do it?
Try to create a stored function (in the database, not in Apex) and pass it P_KPI value as a parameter. Then test what you get, as well as the result. When working with dynamic SQL, it is a good idea to DBMS_OUTPUT.PUT_LINE the resulting statement (that would be SQL_STMT in your example), copy/paste it into SQL*Plus (or any other tool you use, such as SQL Developer) and see whether it works correctly.
For example:
CREATE OR REPLACE FUNCTION f_stmt (par_kpi IN NUMBER)
RETURN VARCHAR2
IS
sql_stmt VARCHAR2 (32767);
calc_clause VARCHAR2 (4000);
BEGIN
SELECT calculation
INTO calc_clause
FROM kpi_types
WHERE id = par_kpi;
sql_stmt :=
'SELECT DATE, '
|| calc_clause
|| ' KPI_VALUE '
|| ' FROM DATA_VALUES '
|| ' WHERE TYPE_ID = '
|| par_kpi
|| ' GROUP BY DATE';
DBMS_OUTPUT.put_line (sql_stmt);
RETURN sql_stmt;
END;

Answer 2

Starting with the stored function suggested by Littlefoot, I was able to use this solution:
http://vincentdeelen.blogspot.com/2014/02/interactive-report-based-on-dynamic-sql.html
I have a page process that creates a collection with the dynamic query string. The charts region SQL now queries from the collection, and I can use all of my page items to filter the data appropriately.