在SQL Server 2008中獲取相同輸出的最簡單方法是什麼？SQL Server 2008中的try_parse
的SQLServer 2012：
select
try_parse(Isnull('123.66',0) as float) as a ,
try_parse(Isnull('.',0) as float) as b
結果
a b
------------
123.66 NULL
的SQLServer 2008： ？
您可以使用此codesnippet應該做你在尋找的東西。 將它添加到更大表格上的選擇應該不是什麼大問題。只需將該變量替換爲代碼列即可。
這裏是例子：
DECLARE @string nvarchar(255)
SET @string = 'Hali€hHalo'
SELECT Substring(
@string,
PATINDEX('%[0-9.]%',@string),
PATINDEX('%[^0-9.]%',
Substring(
@string,
PATINDEX(
'%[0-9.]%',
@string
),
LEN(@string)
)
)-1
)
GO
結果：空字符串，但可以用一個情況下，如果需要一個NULL被更換時... IS NULL ELSE THEN NULL ... END。
的與數字的變量同樣的事情。
DECLARE @string nvarchar(255)
SET @string = 'Hali123.10€hHalo'
SELECT Substring(
@string,
PATINDEX('%[0-9.]%',@string),
PATINDEX('%[^0-9.]%',
Substring(
@string,
PATINDEX(
'%[0-9.]%',
@string
),
LEN(@string)
)
)-1
)
GO
結果：123.10
最好的問候， 離子
我可以得到一個答案，爲什麼你downvote解決方案？ – Ionic
'TRY_PARSE'不僅僅是一種舒適功能，這可以通過複製部分功能所需的複雜代碼引起的*不適感來證明。如果有一千個分隔符會怎樣？如果例如小數點分隔符是逗號，如在許多歐洲國家那樣呢？它可能會更簡單/更安全（但更慢）嘗試'cast'並捕獲失敗，例如在標量函數中，而不是嘗試複製'TRY_PARSE'的行爲。只有CLR UDF實際上可以在SQL Server 2008中提供相同的功能 –
那麼如果你有SQL Server 2008而不是SQL Server 2012，那麼試試你的TRY_PARSE。但它不會工作。有些公司將無法升級到SQL Server 2012，因爲許可證模式非常差。這樣你就不能使用try_parse並且需要一個解決方法 - 就像提問者那樣。可能很容易檢查分隔符並適應。您也可以在無法轉換的行上使用此語句。 – Ionic
TRY_PARSE做兩件事情 - 用特定的文化解析文本如果轉換失敗則返回NULL。在SQL Server 2008中您可以使用ISNUMERIC功能，如shown here效仿這一部分功能：
select
CASE
WHEN ISNUMERIC(@input)=1 and LEFT(@input,1) LIKE'[0-9]' THEN
CAST(@input as float)
ELSE
NULL
END,
ISNUMERIC返回1甚至.或」 0.5' ，雖然，造成投失敗。這是通過第二次檢查覆蓋LEFT(@input,1) LIKE'[0-9]'
您可以創建一個標量函數，所以你沒有這一切要投射的值每次都輸入：
CREATE FUNCTION try_parse_float(@input varchar(20))
returns float
AS
begin
declare @result float;
select @result=CASE
WHEN ISNUMERIC(@input)=1 and LEFT(@input,1) LIKE'[0-9]'
THEN CAST(@input as float)
ELSE NULL
END;
return @result;
end
所以，你可以寫
SELECT dbo.try_parse_float('123,4'), try_parse_float('.')
----- ----
123.4 NULL
編輯
最安全，最快捷的選擇是簡單地避免存儲數字VA在數據庫中作爲文本提示，確保在加載過程中解析數據。例如，.NET和OLEDB提供程序可以解析"123-"到-123，而T-SQL不能。
在加載過程中處理自定義格式（例如，在將表單數據保存到數據庫之前調用float.TryParseExact或在SSIS ETL腳本中使用C＃腳本組件），處理自定義格式也容易得多。
我寫了一個有用的標量函數來模擬SQL SERVER 2012的TRY_CAST功能在SQL Server 2008中。
dbo.TRY_CAST(Expression, Data_Type, ReturnValueIfErrorCast)
兩個與TRY_CAST功能FO SQL Server 2012的主要區別是，你必須通過3個參數，你 必須另外進行明確的轉換或轉換成字段。 但是，它仍然非常有用，因爲如果CAST未正確執行，它允許您返回默認值 。
功能碼：
DECLARE @strSQL NVARCHAR(1000)
IF NOT EXISTS (SELECT * FROM dbo.sysobjects WHERE id = OBJECT_ID(N'[dbo].[TRY_CAST]'))
BEGIN
SET @strSQL = 'CREATE FUNCTION [dbo].[TRY_CAST]() RETURNS INT AS BEGIN RETURN 0 END'
EXEC sys.sp_executesql @strSQL
END
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
/*
------------------------------------------------------------------------------------------------------------------------
Description:
Syntax
---------------
dbo.TRY_CAST(Expression, Data_Type, ReturnValueIfErrorCast)
+---------------------------+-----------------------+
| Expression | VARCHAR(8000) |
+---------------------------+-----------------------+
| Data_Type | VARCHAR(8000) |
+---------------------------+-----------------------+
| ReturnValueIfErrorCast | SQL_VARIANT = NULL |
+---------------------------+-----------------------+
Arguments
---------------
expression
The value to be cast. Any valid expression.
Data_Type
The data type into which to cast expression.
ReturnValueIfErrorCast
Value returned if cast fails or is not supported. Required. Set the DEFAULT value by default.
Return Type
----------------
Returns value cast to SQL_VARIANT type if the cast succeeds; otherwise, returns null if the parameter @pReturnValueIfErrorCast is set to DEFAULT,
or that the user indicates.
Remarks
----------------
dbo.TRY_CAST function simulates the TRY_CAST function reserved of SQL SERVER 2012 for using in SQL SERVER 2008.
dbo.TRY_CAST function takes the value passed to it and tries to convert it to the specified Data_Type.
If the cast succeeds, dbo.TRY_CAST returns the value as SQL_VARIANT type; if the cast doesn´t succees, null is returned if the parameter @pReturnValueIfErrorCast is set to DEFAULT.
If the Data_Type is unsupported will return @pReturnValueIfErrorCast.
dbo.TRY_CAST function requires user make an explicit CAST or CONVERT in ANY statements.
This version of dbo.TRY_CAST only supports CAST for INT, DATE, NUMERIC and BIT types.
Examples
====================================================================================================
--A. Test TRY_CAST function returns null
SELECT
CASE WHEN dbo.TRY_CAST('6666666166666212', 'INT', DEFAULT) IS NULL
THEN 'Cast failed'
ELSE 'Cast succeeded'
END AS Result;
GO
--B. Error Cast With User Value
SELECT
dbo.TRY_CAST('2147483648', 'INT', DEFAULT) AS [Error Cast With DEFAULT],
dbo.TRY_CAST('2147483648', 'INT', -1) AS [Error Cast With User Value],
dbo.TRY_CAST('2147483648', 'INT', NULL) AS [Error Cast With User NULL Value];
GO
--C. Additional CAST or CONVERT required in any assignment statement
DECLARE @IntegerVariable AS INT
SET @IntegerVariable = CAST(dbo.TRY_CAST(123, 'INT', DEFAULT) AS INT)
SELECT @IntegerVariable
GO
IF OBJECT_ID('tempdb..#temp') IS NOT NULL
DROP TABLE #temp
CREATE TABLE #temp (
Id INT IDENTITY
, FieldNumeric NUMERIC(3, 1)
)
INSERT INTO dbo.#temp (FieldNumeric)
SELECT CAST(dbo.TRY_CAST(12.3, 'NUMERIC(3,1)', 0) AS NUMERIC(3, 1));--Need explicit CAST on INSERT statements
SELECT *
FROM #temp
DROP TABLE #temp
GO
--D. Supports CAST for INT, DATE, NUMERIC and BIT types.
SELECT dbo.TRY_CAST(2147483648, 'INT', 0) AS [Cast failed]
, dbo.TRY_CAST(2147483647, 'INT', 0) AS [Cast succeeded]
, SQL_VARIANT_PROPERTY(dbo.TRY_CAST(212, 'INT', 0), 'BaseType') AS [BaseType];
SELECT dbo.TRY_CAST('AAAA0101', 'DATE', DEFAULT) AS [Cast failed]
, dbo.TRY_CAST('20160101', 'DATE', DEFAULT) AS [Cast succeeded]
, SQL_VARIANT_PROPERTY(dbo.TRY_CAST('2016-01-01', 'DATE', DEFAULT), 'BaseType') AS [BaseType];
SELECT dbo.TRY_CAST(1.23, 'NUMERIC(3,1)', DEFAULT) AS [Cast failed]
, dbo.TRY_CAST(12.3, 'NUMERIC(3,1)', DEFAULT) AS [Cast succeeded]
, SQL_VARIANT_PROPERTY(dbo.TRY_CAST(12.3, 'NUMERIC(3,1)', DEFAULT), 'BaseType') AS [BaseType];
SELECT dbo.TRY_CAST('A', 'BIT', DEFAULT) AS [Cast failed]
, dbo.TRY_CAST(1, 'BIT', DEFAULT) AS [Cast succeeded]
, SQL_VARIANT_PROPERTY(dbo.TRY_CAST('123', 'BIT', DEFAULT), 'BaseType') AS [BaseType];
GO
--E. B. TRY_CAST return NULL on unsupported data_types
SELECT dbo.TRY_CAST(4, 'xml', DEFAULT) AS [unsupported];
GO
====================================================================================================
Responsible: Javier Pardo
Date: diciembre 29/2016
WB tests: Javier Pardo
------------------------------------------------------------------------------------------------------------------------
*/
ALTER FUNCTION dbo.TRY_CAST
(
@pExpression AS VARCHAR(8000),
@pData_Type AS VARCHAR(8000),
@pReturnValueIfErrorCast AS SQL_VARIANT = NULL
)
RETURNS SQL_VARIANT
AS
BEGIN
--------------------------------------------------------------------------------
-- INT
--------------------------------------------------------------------------------
IF @pData_Type = 'INT'
BEGIN
IF ISNUMERIC(@pExpression) = 1
BEGIN
DECLARE @pExpressionINT AS FLOAT = CAST(@pExpression AS FLOAT)
IF @pExpressionINT BETWEEN - 2147483648.0 AND 2147483647.0
BEGIN
RETURN CAST(@pExpressionINT as INT)
END
ELSE
BEGIN
RETURN @pReturnValueIfErrorCast
END --FIN IF @pExpressionINT BETWEEN - 2147483648.0 AND 2147483647.0
END
ELSE
BEGIN
RETURN @pReturnValueIfErrorCast
END -- FIN IF ISNUMERIC(@pExpression) = 1
END -- FIN IF @pData_Type = 'INT'
--------------------------------------------------------------------------------
-- DATE
--------------------------------------------------------------------------------
IF @pData_Type = 'DATE'
BEGIN
IF ISDATE(@pExpression) = 1
BEGIN
DECLARE @pExpressionDATE AS DATE = cast(@pExpression AS DATE)
RETURN cast(@pExpressionDATE as DATE)
END
ELSE
BEGIN
RETURN @pReturnValueIfErrorCast
END --FIN IF ISDATE(@pExpression) = 1
END --FIN IF @pData_Type = 'DATE'
--------------------------------------------------------------------------------
-- NUMERIC
--------------------------------------------------------------------------------
IF @pData_Type LIKE 'NUMERIC%'
BEGIN
IF ISNUMERIC(@pExpression) = 1
BEGIN
DECLARE @TotalDigitsOfType AS INT = SUBSTRING(@pData_Type,CHARINDEX('(',@pData_Type)+1, CHARINDEX(',',@pData_Type) - CHARINDEX('(',@pData_Type) - 1)
, @TotalDecimalsOfType AS INT = SUBSTRING(@pData_Type,CHARINDEX(',',@pData_Type)+1, CHARINDEX(')',@pData_Type) - CHARINDEX(',',@pData_Type) - 1)
, @TotalDigitsOfValue AS INT
, @TotalDecimalsOfValue AS INT
, @TotalWholeDigitsOfType AS INT
, @TotalWholeDigitsOfValue AS INT
SET @pExpression = REPLACE(@pExpression, ',','.')
SET @TotalDigitsOfValue = LEN(REPLACE(@pExpression, '.',''))
SET @TotalDecimalsOfValue = CASE Charindex('.', @pExpression)
WHEN 0
THEN 0
ELSE Len(Cast(Cast(Reverse(CONVERT(VARCHAR(50), @pExpression, 128)) AS FLOAT) AS BIGINT))
END
SET @TotalWholeDigitsOfType = @TotalDigitsOfType - @TotalDecimalsOfType
SET @TotalWholeDigitsOfValue = @TotalDigitsOfValue - @TotalDecimalsOfValue
-- The total digits can not be greater than the p part of NUMERIC (p, s)
-- The total of decimals can not be greater than the part s of NUMERIC (p, s)
-- The total digits of the whole part can not be greater than the subtraction between p and s
IF (@TotalDigitsOfValue <= @TotalDigitsOfType) AND (@TotalDecimalsOfValue <= @TotalDecimalsOfType) AND (@TotalWholeDigitsOfValue <= @TotalWholeDigitsOfType)
BEGIN
DECLARE @pExpressionNUMERIC AS FLOAT
SET @pExpressionNUMERIC = CAST (ROUND(@pExpression, @TotalDecimalsOfValue) AS FLOAT)
RETURN @pExpressionNUMERIC --Returns type FLOAT
END
else
BEGIN
RETURN @pReturnValueIfErrorCast
END-- FIN IF (@TotalDigitisOfValue <= @TotalDigits) AND (@TotalDecimalsOfValue <= @TotalDecimals)
END
ELSE
BEGIN
RETURN @pReturnValueIfErrorCast
END --FIN IF ISNUMERIC(@pExpression) = 1
END --IF @pData_Type LIKE 'NUMERIC%'
--------------------------------------------------------------------------------
-- BIT
--------------------------------------------------------------------------------
IF @pData_Type LIKE 'BIT'
BEGIN
IF ISNUMERIC(@pExpression) = 1
BEGIN
RETURN CAST(@pExpression AS BIT)
END
ELSE
BEGIN
RETURN @pReturnValueIfErrorCast
END --FIN IF ISNUMERIC(@pExpression) = 1
END --IF @pData_Type LIKE 'BIT'
--------------------------------------------------------------------------------
-- FLOAT
--------------------------------------------------------------------------------
IF @pData_Type LIKE 'FLOAT'
BEGIN
IF ISNUMERIC(REPLACE(REPLACE(@pExpression, CHAR(13), ''), CHAR(10), '')) = 1
BEGIN
RETURN CAST(@pExpression AS FLOAT)
END
ELSE
BEGIN
IF REPLACE(@pExpression, CHAR(13), '') = '' --Only white spaces are replaced, not new lines
BEGIN
RETURN 0
END
ELSE
BEGIN
RETURN @pReturnValueIfErrorCast
END --IF REPLACE(@pExpression, CHAR(13), '') = ''
END --FIN IF ISNUMERIC(@pExpression) = 1
END --IF @pData_Type LIKE 'FLOAT'
--------------------------------------------------------------------------------
-- Any other unsupported data type will return NULL or the value assigned by the user to @pReturnValueIfErrorCast
--------------------------------------------------------------------------------
RETURN @pReturnValueIfErrorCast
END
現在只支持數據類型INT，DATE，NUMERIC，BIT和FLOAT。你可以在下面的鏈接中找到這段代碼的最後一個版本，我們互相幫助改進它。 TRY_CAST功能的SQL Server 2008https://gist.github.com/jotapardo/800881eba8c5072eb8d99ce6eb74c8bb
您必須編寫一個UDF複製在SQL Server 2008 try_parse的行爲，因爲這個功能在SQL Server中添加了2012版 –
如果有一個簡單的方法來達到同樣的在2008年，他們不會將它添加到2012年。 –
您可以嘗試使用'ISNUMERIC'來檢查在投射前數據是否爲數字，如[此處顯示]（http://stackoverflow.com/questions/2000045/tsql- （@text AS INT）ELSE NULL END' –