次の SQL クエリを最適化する方法を探しています。私はMS SQL Server 2008を使用しています。外部結合を統合する方法があれば速度が上がると考えています...誰かが何か意見を持っていれば、それは大歓迎です。ありがとう
SELECT employee.employee_id,
coalesce (room.ship_id, ship.ship_id) AS ship_id,
SUBSTRING (employee.service_id, 0, 6) AS cost_code,
employee_station.room_cat AS nws_room_cat
FROM employee
LEFT OUTER JOIN room
ON employee.ship_id = room.ship_id
AND employee.floor_id = room.floor_id
AND employee.room_id = room.room_id
LEFT OUTER JOIN ship
ON employee.ship_id = ship.ship_id
LEFT OUTER JOIN employee_station
ON COALESCE (ship.property_type, '') =
COALESCE (employee_station.property_type, '')
AND COALESCE (room.work_center_id, '') = COALESCE (employee_station.work_center_id, '')
AND COALESCE (employee.pay_plan, '') =
COALESCE (employee_station.pay_plan, '')
AND COALESCE (employee.employee_type, '') =
COALESCE (employee_station.employee_type, '')
AND COALESCE (SUBSTRING (employee.service_id, 0, 6), '') =
COALESCE (employee_station.cost_code, '')
LEFT OUTER JOIN roomtype
ON room.room_type = roomtype.room_type
LEFT OUTER JOIN dp
ON employee.service_id = dp.service_id
注: ここでは、わかりやすくするために、SELECT ステートメントの多くのフィールドを意図的に省略しています。したがって、roomtype と dp テーブルは実際に使用されています...