Please help me write a query

[Nikolas Everett <nik9000@xxxxxxxxx>]

Say I have a table that stores state transitions over time like so:

id, transitionable_id, state1, state2, timestamp

I'm trying to write a query that coalesces changes in state2 away to produce just a list of transitions of state1.  I guess it would look something like

SELECT state1, FIRST(timestamp)

FROM table

but I have no idea how to aggregate just the repeated state1 rows.