Casting Varchar2 to interval - oracle

Question

I have a configuration table such that I want to delete a row if the record_tm is over a certain configurable time (config_recordtrim_hrs). In other words, the variable recordtrim_config comes from another table where somebody writes a value (e.g. 24 for 24 hours) after which a record will be deleted.
DECLARE
recordtrim_flag configs_table.value%type;
recordtrim_config configs_table.value%type;
recordtrim_interval interval;
BEGIN
SELECT configs_table.value INTO recordtrim_flag FROM configs_table WHERE configs_table.name = 'enable_recordtrim';
SELECT configs_table.value INTO recordtrim_config FROM configs_table WHERE configs_table.name = 'config_recordtrim_hrs';
SELECT CAST (recordtrim_config AS interval) INTO recordtrim_interval;
IF (recordtrim_flag = 'T') THEN
DELETE FROM main_records WHERE record_tm + recordtrim_interval < current_timestamp;
END IF;
END;
This code throws an error at the line where I try to cast recordtrim_config as an interval. How do I fix this?
EDIT: My error:
Error report: ORA-06550: line 8, column 40: PL/SQL: ORA-30089: missing
or invalid ORA-06550: line 8, column 1: PL/SQL: SQL
Statement ignored
EDIT 2: New Code:
DECLARE
recordtrim_flag configs_table.value%type;
recordtrim_config configs_table.value%type;
recordtrim_interval interval;
BEGIN
SELECT configs_table.value INTO recordtrim_flag FROM configs_table WHERE configs_table.name = 'enable_recordtrim';
SELECT configs_table.value INTO recordtrim_config FROM configs_table WHERE configs_table.name = 'config_recordtrim_hrs';
recordtrim_interval := NUMTODSINTERVAL (recordtrim_config, 'HOUR');
IF (recordtrim_flag = 'T') THEN
DELETE FROM main_records WHERE record_tm + recordtrim_interval < current_timestamp;
END IF;
END;
New Error at line 11, recordtrim_interval is an invalid identifier

Answer 1

The immediate cause of the error is that you've got just interval instead of the type, i.e. interval day to second. You also have to select from something - which can be from dual here, though a straight assignment is cleaner.
You can't cast it directly if it's a single number. Instead you can use the numtodsinterval function:
recordtrim_interval := NUMTODSINTERVAL (recordtrim_config, 'HOUR');
e.g.
set serveroutput on
declare
recordtrim_config varchar2(4) := '24';
recordtrim_interval interval day to second;
begin
recordtrim_interval := NUMTODSINTERVAL (recordtrim_config, 'HOUR');
dbms_output.put_line(recordtrim_interval);
end;
/
anonymous block completed
+01 00:00:00.000000
Or select that straight into the variable from the table.
If you need more complicated values, not a simple value that represents a number of hours - and if that was the case you'd store it as a number I assume - then if you store it in a suitable format, you can cast it, or use the to_dsinterval function instead; any of these give the same result:
declare
recordtrim_config varchar2(10) := '0 2:30:00';
recordtrim_interval interval day to second;
begin
recordtrim_interval := TO_DSINTERVAL (recordtrim_config);
dbms_output.put_line(recordtrim_interval);
SELECT CAST (recordtrim_config AS interval day to second)
INTO recordtrim_interval from dual;
dbms_output.put_line(recordtrim_interval);
recordtrim_interval := CAST (recordtrim_config AS interval day to second);
dbms_output.put_line(recordtrim_interval);
end;
/
anonymous block completed
+00 02:30:00.000000
+00 02:30:00.000000
+00 02:30:00.000000
In your edited question, the ORA-00904: "RECORDTRIM_INTERVAL": invalid identifier is only the last error in the list. Look back a bit and you'll see:
ORA-06550: line 4, column 21:
PLS-00201: identifier 'INTERVAL' must be declared
... followed by some other errors where you try to use the variable. Your declaration of the variable has to be:
recordtrim_interval interval day to second;
There is no 'interval' data type; they are interval year to month and interval day to second.