Transform table data

I have a table A of data:

[id][parameter][value]
-----------------------------
[01][aa][20]
[02][bb][21]
[03][cc][22]
[04][aa][23]
[05][bb][24]
[06][cc][25]
[07][aa][26]
[08][bb][27]
[09][cc][28]

that i would like to convert into the following table B:

[key][aa][bb][cc]
---------------------
[001][20][21][22]
[002][23][24][25]
[003][26][27][28]

I program in PHP5, and would use arrays to transform it. But, I
believe that if table A is large, I am going to run out of working
memory or having a server timed out, before I can finish the task. Can
I make postgresql perform this task instead?

I am not sure where to find any reference to do this in postgresql.

Thanks in advance.
--
Jason Tan Boon Teck