FOR LOOP with WHERE clause - oracle

Question

This question has been posed before but not specifically for Oracle database.
Can a FOR LOOP be filtered with WHERE clause? For example I would like to do something like:
--LOG ERRORS
FOR err in c_errors WHERE trx_type='CYCLE_COUNT'
LOOP
...do some stuff
END LOOP;
This code gives error:
PLS-00103: Encountered the symbol "WHERE" when expecting one of the following ...
Is there proper syntax for this?
Here is the cursor definition. It grabs cycle count and adjustment transaction types. But in the log errors section mentioned above, I only want to report on cycle count errors. Sure I could use separate cursors, but was trying to accomplish using one.
CURSOR c_errors IS
SELECT DISTINCT CC_ENTRY_INTERFACE_ID INTERFACE_ID
,ERROR_MESSAGE
,creation_date
,LAST_UPDATE_DATE
,'CYCLE_COUNT' TRX_TYPE
FROM mtl_cc_interface_errors
UNION
SELECT DISTINCT TRANSACTION_INTERFACE_ID
,ERROR_EXPLANATION
,CREATION_DATE
,LAST_UPDATE_DATE
,'ADJUSTMENT'
FROM mtl_transactions_interface
WHERE process_flag=3
AND error_code IS NOT NULL
ORDER BY last_update_date DESC;

Answer 1

FOR err in c_errors WHERE trx_type='CYCLE_COUNT'
This is semantically incorrect.
What you can do, as one of the options, is to create a parameterized cursor.
Here is an example:
Case #1: Parameter is null. All rows returned
set serveroutput on;
declare
cursor l_cursor ( param1 varchar2) is
select *
from (
select level as c1
, 'cycle_count' as trx_type
from dual
connect by level < 3
union all
select level as c1
, 'adjustemnt' as trc_type
from dual
connect by level < 3
) q
where param1 is null
or trx_type = param1;
begin
-- param1 = null. No filter applied
for r in l_cursor(null) loop
dbms_output.put_line('C1: ' || to_char(r.c1) || '; ' ||
'TRX_TYPE: ' || r.trx_type);
end loop;
end;
Result:
CNT: 1; TRX_TYPE: cycle_count
CNT: 2; TRX_TYPE: cycle_count
CNT: 1; TRX_TYPE: adjustemnt
CNT: 2; TRX_TYPE: adjustemnt
Case #1: Filtering by TRX_TYPE
set serveroutput on;
declare
cursor l_cursor ( param1 varchar2) is
select *
from (
select level as c1
, 'cycle_count' as trx_type
from dual
connect by level < 3
union all
select level as c1
, 'adjustemnt' as trc_type
from dual
connect by level < 3
) q
where param1 is null
or trx_type = param1;
begin
-- param1 = 'cycle_count'
for r in l_cursor('cycle_count') loop
dbms_output.put_line('C1: ' || to_char(r.c1) || '; ' ||
'TRX_TYPE: ' || r.trx_type);
end loop;
end;
Result:
C1: 1; TRX_TYPE: cycle_count
C1: 2; TRX_TYPE: cycle_count

Answer 2

Nick's answer it's a nice explanation.
Here is another example of how to use it, by declaring the cursor inline with the FOR syntax:
BEGIN
FOR r_product IN (
SELECT
product_name, list_price
FROM
products
WHERE list_price > 120
ORDER BY list_price DESC
)
LOOP
dbms_output.put_line( r_product.product_name ||
': $' ||
r_product.list_price );
END LOOP;
END;
Source:
https://www.oracletutorial.com/plsql-tutorial/plsql-cursor-for-loop/