oracle sql - finding entries with dates (start/end column) overlap -

so data this:

id | start_date       | end_date         |  uid  | canceled ------------------------------------------------- 44 | 2015-10-20 22:30 | 2015-10-20 23:10 | 'one' | 52 | 2015-10-20 23:00 | 2015-10-20 23:30 | 'one' | 66 | 2015-10-21 13:00 | 2015-10-20 13:30 | 'two' |  

there more 100k of these entries.

we can see start_date of second entry overlaps end_date of first entry. when dates overlap, entries lower id should marked true in 'canceled' column.

i tried queries take long time i'm not sure if work. want cover overlaping cases seems slow down.

i 1 responsible inserting/updating these entries using pl/sql

update table set column = 'value' id = '44';    if sql%rowcount = 0         insert values(...)    end if 

so maybe in step. tables updated/inserted using 1 big pl/sql created dynamically rows either updated or new ones inserted once again seems slow.

and of sql 'dialects' oracle 1 cryptic had chance work with. ideas?

edit: forgot 1 important detail, there 1 more column (uid) matched, update above

i start query:

update table t     set cancelled = true     exists (select 1                   table t2                   t.end_date > t2.start_date ,                         t.uid = t2.uid ,                         t.id < t2.id                  ) 

an index on table(uid, start_date, id) might help.

as note: much easier when create table, because can use lag().