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
答案 0 :(得分:3)
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
答案 1 :(得分: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)
)
)
答案 2 :(得分:1)
步骤1是单独运行每个选择并查看瓶颈在哪里。
答案 3 :(得分:0)
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?
答案 4 :(得分:0)
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
答案 5 :(得分:0)
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
答案 6 :(得分:0)
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