2011/9/13 Dianna Harter <dhar...@mynewplace.com>:
Hi,
> [snip]
> Any suggestions to get the order by to occur first then the partition by or
> maybe there another approach that I could use?
I tried to write the query without using the window:
SELECT `X`.`consumer_id`, `X`.`move_date` , `X`.`history_timestamp` ,
MIN( `Y`.`history_timestamp` ) AS `start_time`
FROM
`Table` AS `X`
JOIN
`Table` AS `Y`
ON `X`.`consumer_id` = `Y`.`consumer_id`
AND `X`.`move_date` = `Y`.`move_date`
AND `X`.`history_timestamp` >= `Y`.`history_timestamp`
LEFT JOIN
`Table` AS `Z`
ON `X`.`consumer_id` = `Z`.`consumer_id`
AND `X`.`move_date` <> `Z`.`move_date`
AND `X`.`history_timestamp` >= `Z`.`history_timestamp`
AND `Y`.`history_timestamp` <= `Z`.`history_timestamp`
WHERE `Z`.`consumer_id` IS NULL
GROUP BY `X`.`consumer_id`, `X`.`move_date` , `X`.`history_timestamp`
ORDER BY `X`.`consumer_id`, `X`.`history_timestamp` ASC
To avoid the LEFT JOIN, you can move the control in the sub-query:
SELECT `X`.`consumer_id`, `X`.`move_date` , `X`.`history_timestamp` ,
MIN( `Y`.`history_timestamp` ) AS `start_time`
FROM
`Table` AS `X`
JOIN
`Table` AS `Y`
ON `X`.`consumer_id` = `Y`.`consumer_id`
AND `X`.`move_date` = `Y`.`move_date`
AND `X`.`history_timestamp` >= `Y`.`history_timestamp`
WHERE NOT EXISTS (
SELECT *
FROM `Table` AS `Z`
WHERE `X`.`consumer_id` = `Z`.`consumer_id`
AND `X`.`move_date` <> `Z`.`move_date`
AND `X`.`history_timestamp` >= `Z`.`history_timestamp`
AND `Y`.`history_timestamp` <= `Z`.`history_timestamp`
)
GROUP BY `X`.`consumer_id`, `X`.`move_date` , `X`.`history_timestamp`
ORDER BY `X`.`consumer_id`, `X`.`history_timestamp` ASC
With Y I select history_timestamp preceding the current row with the
same move_date.
With Z I verify that no changes have occurred to move_date between
X.history_timestamp and Y.history_timestamp.
Ciao!
Nicoletta
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