如何在SQL Server 08中优化这个极其低效的用户定义函数

Is there anyway to optimize this horrible inefficient UDF in SQL Server 08. I am fairly new to UDF's and especially looking at them for optimizations.

有没有在SQL Server 08中优化这个可怕的低效UDF。我对UDF很新,特别是看它们进行优化。

UPDATE: Should I be sending a column to a function like this if I wanted to perform it on each row and each column in a query? Is there a better way to go about this?

更新:如果我想在查询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?

Thank You

** @value(float) and @fieldname(varchar(40)) are input parameters **

** @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

7 个解决方案

#1

If you can join the three tables based on PK/FK relationships you could get the query down to a single select. If not, the only immediately obvious optimization is to assign @FRM and @TO in a single select statement:

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

#2

A classical candidate for a inline table function...

内联表函数的经典候选者......

Something like:

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)
        )
)

#3

Step 1 would be to run each select individually and see where the bottleneck is.

第1步是单独运行每个选择,看看瓶颈在哪里。

#4

One small thing you can do:

你能做的一件小事:

 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

If I read the correctly this would be the same as:

如果我正确阅读,这将是:

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

 from dbo.UNIT_TYPES where [UT_ID]=@UT

Why run a select twice on the same record?

为什么在同一条记录上运行两次选择?

#5

This needs to rewritten using JOIN's:

这需要使用JOIN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

#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

#7

You can try this as all one query:

你可以尝试这个作为所有一个查询:

--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

#1