Question

无论如何都要在SQL Server 08中优化这个可怕的低效UDF。我是UDF的新手，特别关注它们的优化。

更新：如果我想在查询中的每一行和每一列上执行它，我应该将列发送到这样的函数吗？有没有更好的方法来解决这个问题？

谢谢

** @value（float）和@fieldname（varchar（40））是输入参数**

BEGIN
  DECLARE @UT integer, @FRM integer, @TO integer, @FACTOR float

  select @UT =  [UF_UT_ID] FROM dbo.UNIT_FIELDS where [UF_FIELD]=@fieldName
  select @FRM = [UT_UN_ID_INTERNAL_UNITS] from dbo.UNIT_TYPES where [UT_ID]=@UT
  select @TO = [UT_UN_ID_DISPLAY_UNITS] from dbo.UNIT_TYPES where [UT_ID]=@UT
  select @FACTOR = [UC_SLOPE] from dbo.UNIT_CONVERSIONS where [UC_UN_ID_UNIT_FROM]=@FRM and [UC_UN_ID_UNIT_TO]=@TO

  -- Return the result of the function dbo.
  RETURN @FACTOR*@value
END

Answer 1

如果您可以根据PK / FK关系加入这三个表，则可以将查询缩减为单个选择。如果没有，唯一明显的优化是在单个select语句中分配@FRM和@TO：

select @FRM = [UT_UN_ID_INTERNAL_UNITS], @TO = [UT_UN_ID_DISPLAY_UNITS] from dbo.UNIT_TYPES where [UT_ID]=@UT

Answer 2

内联表函数的经典候选者......

类似的东西：

ALTER FUNCTION fnName(@value float, @fieldName VARCHAR(100))
RETURNS TABLE 
AS
RETURN 
(
    SELECT @value * 
        (SELECT conv.[UC_SLOPE] from dbo.UNIT_CONVERSIONS conv
        JOIN dbo.UNIT_TYPES UT_UN_ID_INTERNAL_UNITS ON where [UC_UN_ID_UNIT_FROM]=UT_UN_ID_INTERNAL_UNITS.[UT_ID]
        JOIN dbo.UNIT_TYPES UT_UN_ID_DISPLAY_UNITS ON where [UC_UN_ID_UNIT_TO]=UT_UN_ID_DISPLAY_UNITS.[UT_ID]
        JOIN dbo.UNIT_FIELDS fields ON (UT_UN_ID_INTERNAL_UNITS.[UT_ID] = fields.[UF_UT_ID]) AND (UT_UN_ID_DISPLAY_UNITS.[UT_ID] = fields.[UF_UT_ID])
        WHERE ([UF_FIELD]=@fieldName)
        )
)

Answer 3

步骤1是单独运行每个选择并查看瓶颈在哪里。

Answer 4

你可以做的一件小事：

 select @FRM = [UT_UN_ID_INTERNAL_UNITS] from dbo.UNIT_TYPES where [UT_ID]=@UT  
 select @TO = [UT_UN_ID_DISPLAY_UNITS] from dbo.UNIT_TYPES where [UT_ID]=@UT

如果我正确阅读，那将与：

相同

 select @TO = [UT_UN_ID_DISPLAY_UNITS],
        @FRM = [UT_UN_ID_INTERNAL_UNITS] 

 from dbo.UNIT_TYPES where [UT_ID]=@UT

为什么要在同一条记录上运行两次选择？

Answer 5

这需要使用JOIN的重写：

SELECT  c.UC_SLOPE * @value
FROM    unit_fields f
JOIN    unit_types t
ON      t.UT_ID = f.UF_UT_ID
JOIN    unit_conversions c
ON      c.UC_UN_ID_UNIT_FROM = t.UT_UN_ID_INTERNAL_UNITS
        AND c.UC_UN_ID_UNIT_TO = t.UT_UN_ID_DISPLAY_UNITS
WHERE   f.UF_FIELD = @field_name

Answer 6

BEGIN
  DECLARE @FACTOR float

    select @factor = UC.UC_SLOPE
      from dbo.UNIT_CONVERSIONS UC,
           dbo.UNIT_TYPES       UT,
           dbo.UNIT_FIELDS      UF
      where UF.UF_FIELD=@fieldName
        and UT.UT_ID = UF.UF_UT_ID
        and UC.UC_UN_ID_UNIT_FROM = UT.UT_UN_ID_INTERNAL_UNITS
        and UC.UC_UN_ID_UNIT_TO = UT.UT_UN_ID_DISPLAY_UNITS


  -- Return the result of the function dbo.
  RETURN @FACTOR*@value
END

Answer 7

您可以尝试以下所有查询：

--Decalre Factor var
DECLARE @FACTOR float

SELECT @FACTOR = [UC_SLOPE] 
FROM dbo.UNIT_CONVERSIONS uc
--Join the Unit Types table to Unit Conversions on the old From & To types
INNER JOIN dbo.UNIT_TYPES ut ON
    ut.[UT_UN_ID_DISPLAY_UNITS] = uc.[UC_UN_ID_UNIT_TO]
    AND ut.[UT_UN_ID_INTERNAL_UNITS] = uc.[UC_UN_ID_UNIT_FROM]
--Join the Unit Files on the Unit Types
INNER JOIN dbo.UNIT_FIELDS uf ON
    uf.[UF_UT_ID] = ut.[UT_ID]
WHERE uf.[UF_FIELD]=@fieldName

-- Return the result of the function dbo.
RETURN @FACTOR*@value

如何在SQL Server 08中优化这种极其低效的用户定义函数

7 个答案: