mysql - GROUP BY for continuous rows in SQL

Question

Given the following table:

ID   State  Date
12   1      2009-07-16 10:00
45   2      2009-07-16 13:00
67   2      2009-07-16 14:40
77   1      2009-07-16 15:00
89   1      2009-07-16 15:30
99   1      2009-07-16 16:00

Question:
How can i GROUP by the field "State", while still maintaining the borders between the state changes?

SELECT MIN(ID) AS ID, State, MIN(Date) AS Date, COUNT(ID) AS Count
FROM table GROUP BY State

results in the following:

ID   State  Date              Count
12   1      2009-07-16 10:00  4
45   2      2009-07-16 13:00  2

but this is the desired output:

ID   State  Date              Count
12   1      2009-07-16 10:00  1
45   2      2009-07-16 13:00  2
77   1      2009-07-16 15:00  3

Is this possible in SQL? I didn't find a solution so far...

Answer 1

SELECT  MIN(id) AS id, MIN(ts) AS ts, MIN(state) AS state, COUNT(*) cnt
FROM    (
        SELECT  @r := @r + (@state != state) AS gn,
                @state := state AS sn,
                s.*
        FROM    (
                SELECT  @r := 0,
                        @state := 0
                ) vars,
                t_state s
        ORDER BY
                ts
        ) q
GROUP BY
        gn

Table creation scripts for testing:

CREATE TABLE t_state (id INT NOT NULL PRIMARY KEY, state INT NOT NULL, ts DATETIME NOT NULL);

INSERT
INTO  t_state
VALUES
(12,   1,      '2009-07-16 10:00'),
(45,   2,      '2009-07-16 13:00'),
(67,   2,      '2009-07-16 14:40'),
(77,   1,      '2009-07-16 15:00'),
(89,   1,      '2009-07-16 15:30'),
(99,   1,      '2009-07-16 16:00');