Oracle: merge two rows

Question

I have a pairs of related rows in my table.

How to merge these rows:

date                         col1 col2
2012-09-11 13:28:21.0000000  A    50
2012-09-11 13:28:21.0000000  A    -50

to one row

date                         col1 col2 col3
2012-09-11 13:28:21.0000000  A    50   -50

if there can be a small difference between two dates (about one seconds and it occurs in 1 of 100 pairs only)? e.g.:

2012-09-11 13:28:21.0000000
2012-09-11 13:28:22.0000000

or in worse case, one second change whole minute:

2012-09-11 13:28:59.0000000
2012-09-11 13:29:00.0000000

update (string column):

how to merge the same lines with an additional col3 with string values?

date                         col1 col2 col4
2012-09-11 13:28:21.0000000  A    50   abc
2012-09-11 13:28:21.0000000  A    -50  def

to:

date                         col1 col2 col3 col5 col6
2012-09-11 13:28:21.0000000  A    50   -50  abc  def

or to:

date                         col1 col2 col3 col5
2012-09-11 13:28:21.0000000  A    50   -50  abc,def

solution (string) (extension of hkutluays answer):

max(case when col2 > 0 then col4 end) col5
max(case when col2 < 0 then col4 end) col6

Answer 1

Not tested but may solve the problem.

select 
round(sysdate,'MI'),col1, sum( case when col2> 0 then col2 else 0 end ) col2,
sum( case when col2 < 0 then col2 else 0 end ) col3
from table
group by round(sysdate,'MI'),col1