How to look for changes in a table that keeps historical data?

Example:

FIE开发者_Go百科LD_1 | DATE
X | 2010-01-01
X | 2010-02-01
X | 2010-03-01
Y | 2010-04-01
Y | 2010-05-01
Y | 2010-05-01

I would like the SELECT to return the following: (a change occurred in FIELD_1) Y | 2010-04-01

Is there an easy way to do this?

Writen for mssql:

declare @t table(field varchar(20), date date)

insert @t values('X', '2010-01-01')
insert @t values('X', '2010-01-02')
insert @t values('X', '2010-01-03')
insert @t values('Y', '2010-01-04')
insert @t values('Y', '2010-01-05')
insert @t values('Y', '2010-01-06')


select b.* from @t a join @t b on dateadd(day, 1, a.date) = b.date
and a.field <> b.field

Result:

field                date
-------------------- ----------
Y                    2010-01-04

It should also work for sybase if you replace @t with your table and ignore the test data