rolling window without aggregation - Mailing list pgsql-sql

Hi SQL experts,

I’ve got a question here, is that possible to implement a window function without aggregation? Any SQL could get below desired result?

For example:

Table input

    date    | id

------------+--------

2014-04-26 | A

2014-05-03 | B

2014-05-10 | C

2014-05-17 | D

2014-05-24 | E

2014-05-31 | F

Expected output, use 2 week roll up as an example:

    date    | id

------------+--------

2014-04-26 | A

2014-05-03 | A

2014-05-03 | B

2014-05-10 | B

2014-05-10 | C

2014-05-17 | C

2014-05-17 | D

2014-05-24 | D

2014-05-24 | E

2014-05-31 | E

2014-05-31 | F

Thanks,

Suya