Pl/Sql array inside a statement - arrays

Question

I'm trying to prepare a function, so I've started this sql sketch to figure out how to manage my situation:
DECLARE
x XMLType;
begin
x := XMLType('<?xml version="1.0"?>
<ROWSET>
<ROW>
<START_DATETIME>29/05/2015 14:23:00</START_DATETIME>
</ROW>
<ROW>
<START_DATETIME>29/05/2015 17:09:00</START_DATETIME>
</ROW>
</ROWSET>');
FOR r IN (
SELECT ExtractValue(Value(p),'/ROW/START_DATETIME/text()') as deleted
FROM TABLE(XMLSequence(Extract(x,'/ROWSET/ROW'))) p
) LOOP
-- do whatever you want with r.name, r.state, r.city
-- dbms_output.put_line( 'TO_DATE('''|| r.deleted ||''', '''|| 'DD/MM/YYYY HH24:MI:SS'')');
dbms_output.put_line( ''''|| r.deleted ||'''');
DELETE FROM MYTABLE a WHERE a.START_DATETIME not in (''''|| r.deleted || '''');
END LOOP;
END;
I've tried different ways to perform the query after the loop has filled the variable but is gaves me a conversion error:
00000 - "a non-numeric character was found where a numeric was expected"
*Cause: The input data to be converted using a date format model was
incorrect. The input data did not contain a number where a number was
required by the format model.
*Action: Fix the input data or the date format model to make sure the
elements match in number and type. Then retry the operation.
Can anybody help me?
thanks!

Answer 1

You're wrapping a string in explicit single quotes; that is making the quotes part of the string itself, which you don't want.
You need to convert the string to a data type, which you are sort of doing in a commented-out section - in that case you do need the extra quotes for your dbms_output() to make it a text literal, and to end up as a valid to_date() call; so you end up with output from that:
TO_DATE('29/05/2015 14:23:00', 'DD/MM/YYYY HH24:MI:SS')
But for your delete though you just need to do:
DELETE FROM MYTABLE a
WHERE a.START_DATETIME not in (to_date(r.deleted, 'DD/MM/YYYY HH24:MI:SS'));
The reference to r.deleted is already a string, so you refer to it directly, with no additional quotes.
You only have a single value though, so at that point in the loop using not in is not necessary and you can use != instead:
DELETE FROM MYTABLE
WHERE START_DATETIME != to_date(r.deleted, 'DD/MM/YYYY HH24:MI:SS');
Your title mentions an array, so perhaps you really intend to put all the values from the XML into a (schema-level type) table collection and then use that in the not in clause, so it removes everything except the dates in your XML. Doing it individually like this will effectively delete everything in the table if there is more than one date in the XML, which also suggests you either want to use an array, and/or actually meant in or = to only remove those.
Incidentally, extractValue() is deprecated, so it would be better to use XMLQuery or XMLTable, e.g.:
FOR r IN (
SELECT *
FROM XMLTable('/ROWSET/ROW/START_DATETIME'
PASSING x COLUMNS deleted VARCHAR2(19) PATH '.')
) LOOP