In article <[EMAIL PROTECTED]>,
george young <gry@ll.mit.edu> writes:
> [PostgreSQL 7.4RC2 on i686-pc-linux-gnu](I know, I know... must upgrade soon)
> I have a table mytable like:
> i | txt
> ---+-------
> 1 | the
> 2 | the
> 3 | rain
> 4 | in
> 5 | mainly
> 6 | spain
> 7 | stays
> 8 | mainly
> 9 | in
> I want to update it, adding a ':' to txt so that each txt value is unique.
> I don't care which entry gets changed. I tried:
> update mytable set txt=mytable.txt || ':' from mytable t2 where
> mytable.txt=t2.txt and mytable.i=t2.i;
> but this updated both duplicated entries.
> Um, there may sometimes be 3 or 4 duplicates, not just two. For these, I can
> add multiple colons, or one each of an assortment of characters, say ':+*&^#'.
> Performance does not matter here. The real table has 30K rows, ~200 dups.
> To clarify, I want to end up with something like:
> 1 | the
> 2 | the:
> 3 | rain
> 4 | in
> 5 | mainly:
> 6 | spain
> 7 | stays
> 8 | mainly
> 9 | in:
Try the following:
UPDATE mytable
SET txt = txt || substring ('::::::::::::::::' for (
SELECT count(*)
FROM mytable t1
WHERE t1.txt = mytable.txt AND t1.i < mytable.i
)::int)
---------------------------(end of broadcast)---------------------------
TIP 6: explain analyze is your friend
