Update From Select statement

Question

I'm very new to Oracle so please bear with me.
I need to Update a table ( T1) with dates selected from another table (T2). However, because of the size of the tables (the second one has upwards of 3,000,000 rows) I have to do it incrementally, say 10k rows at a time. However, there's no field in T1 that I can use as a flag to say the row's been updated. But I do have an ascending numeric field that I can do a Max() function on. My thought was to capture the max numeric function in local variable and use it in a where clause so I only get the rows I need to update. Pseudo-ish code follows:
DECLARE
mDoc NUMBER
maxNum NUMBER
BEGIN
mDoc = 0;
SELECT MAX(doc_id_n) INTO maxNum FROM T2;
WHILE NOT mDoc > maxNum
LOOP
SELECT MAX(doc_id_n) INTO mDoc FROM T2
WHERE doc_id_n > mDoc AND rownum < 10001;
UPDATE T1 SET scan_d =
(select to_date(t.ddate,'MM/DD/YYYY') as ndate
from T2 t, T1 i
where i.stor_rep_id = 'HRPAYROLL1' and
t.doc_id_n = i.doc_id_n and rownum < 10001
AND NOT t.doc_id_n > mDoc
ORDER BY t.doc_id_n)
END LOOP;
END;

Answer 1

You say:
<However, there's no field in T1 that I can use as a flag to say the row's been updated.
That's fine, you needn't nor might you want to do this incrementally. Instead, what basis or values in table(T1) are you using to determine which rows are updated? For example, you might want to use a particular field as your 'filter' between the two tables. Still it's not fun :)
UPDATE T1 SET date_column = (SELECT inserted_date FROM T2 WHERE customer = 'ABC')
WHERE customer = 'ABC';
UPDATE T1 SET date_column = (SELECT inserted_date FROM T2 WHERE customer = 'XYZ')
WHERE customer = 'XYZ';
Hope this helps.