我有一个使用表值函数的存储过程，该函数在 9 秒内执行。如果我更改表值函数并删除 where 子句，则存储过程将在 3 秒内执行。如果我添加 where 子句，查询仍会在 3 秒内执行。
我查看了执行计划，似乎在删除 where 子句后，执行计划包括并行性，并且我的 2 个表的扫描计数从 50000 和 65000 下降到 5 和 3。添加 where 子句后回来，优化的执行计划仍然运行，除非我运行 DBCC FREEPROCCACHE。
问题 1. 为什么只有在我第一次删除 where 子句时，SQL Server 才会开始对两个查询都使用优化的执行计划？
- 有没有办法强制 SQL Server 使用这个执行计划？
此外，这是一个参数化的一体式查询，它在 where 子句中使用 (Parameter is null or Parameter)，我认为这对性能不利。
RETURNS TABLE
AS
RETURN
(
SELECT TOP (@PageNumber * @PageSize)
CASE
WHEN @SortOrder = 'Expensive' THEN ROW_NUMBER() OVER (ORDER BY SellingPrice DESC)
WHEN @SortOrder = 'Inexpensive' THEN ROW_NUMBER() OVER (ORDER BY SellingPrice ASC)
WHEN @SortOrder = 'LowMiles' THEN ROW_NUMBER() OVER (ORDER BY Mileage ASC)
WHEN @SortOrder = 'HighMiles' THEN ROW_NUMBER() OVER (ORDER BY Mileage DESC)
WHEN @SortOrder = 'Closest' THEN ROW_NUMBER() OVER (ORDER BY P1.Distance ASC)
WHEN @SortOrder = 'Newest' THEN ROW_NUMBER() OVER (ORDER BY [Year] DESC)
WHEN @SortOrder = 'Oldest' THEN ROW_NUMBER() OVER (ORDER BY [Year] ASC)
ELSE ROW_NUMBER() OVER (ORDER BY InventoryID ASC)
END as rn,
P1.InventoryID,
P1.SellingPrice,
P1.Distance,
P1.Mileage,
Count(*) OVER () RESULT_COUNT,
dimCarStatus.[year]
FROM (SELECT InventoryID, SellingPrice, Zip.Distance, Mileage, ColorKey, CarStatusKey, CarKey FROM facInventory
JOIN @ZipCodes Zip
ON Zip.DealerKey = facInventory.DealerKey) as P1
JOIN dimColor
ON dimColor.ColorKey = P1.ColorKey
JOIN dimCarStatus
ON dimCarStatus.CarStatusKey = P1.CarStatusKey
JOIN dimCar
ON dimCar.CarKey = P1.CarKey
WHERE
(@ExteriorColor is NULL OR dimColor.ExteriorColor like @ExteriorColor) AND
(@InteriorColor is NULL OR dimColor.InteriorColor like @InteriorColor) AND
(@Condition is NULL OR dimCarStatus.Condition like @Condition) AND
(@Year is NULL OR dimCarStatus.[Year] like @Year) AND
(@Certified is NULL OR dimCarStatus.Certified like @Certified) AND
(@Make is NULL OR dimCar.Make like @Make) AND
(@ModelCategory is NULL OR dimCar.ModelCategory like @ModelCategory) AND
(@Model is NULL OR dimCar.Model like @Model) AND
(@Trim is NULL OR dimCar.Trim like @Trim) AND
(@BodyType is NULL OR dimCar.BodyType like @BodyType) AND
(@VehicleTypeCode is NULL OR dimCar.VehicleTypeCode like @VehicleTypeCode) AND
(@MinPrice is NULL OR P1.SellingPrice >= @MinPrice) AND
(@MaxPrice is NULL OR P1.SellingPrice < @MaxPrice) AND
(@Mileage is NULL OR P1.Mileage < @Mileage)
ORDER BY
CASE
WHEN @SortOrder = 'Expensive' THEN -SellingPrice
WHEN @SortOrder = 'Inexpensive' THEN SellingPrice
WHEN @SortOrder = 'LowMiles' THEN Mileage
WHEN @SortOrder = 'HighMiles' THEN -Mileage
WHEN @SortOrder = 'Closest' THEN P1.Distance
WHEN @SortOrder = 'Newest' THEN -[YEAR]
WHEN @SortOrder = 'Oldest' THEN [YEAR]
ELSE InventoryID
END
)