January 10, 2012 at 8:05 am
Hi All,
I have a very interesting situation. I am pulling following string (see Coulmn1) using substring,replace..etc. from the varchar(5000). I want to execute it as a mathematical expression and want the result shown in Column2.
Column1 --------------- Coulmn2
2 * 2+1 * 7 --------------- 11
1 * 1+2 * 4 --------------- 9
1 * 1+2 * 4+1 * 4 --------- 13
January 10, 2012 at 8:12 am
What about operator precedence? If it needs to be calculated from left to right, it would be easy with string operations. Operator precedence will make it little complicated.
Please provide us DDL, sample data to play with.
January 10, 2012 at 8:17 am
BEGIN TRAN
CREATE TABLE yourTable (yourTableID INT IDENTITY, column1 VARCHAR(500), column2 VARCHAR(500))
INSERT INTO yourTable (column1)
SELECT '2 * 2+1 * 7'
UNION ALL SELECT '1 * 1+2 * 4'
UNION ALL SELECT '1 * 1+2 * 4+1 * 4'
DECLARE @SQL AS VARCHAR(MAX)
SELECT @SQL = COALESCE(@SQL + ';' + CHAR(10),'') +
'UPDATE yourTable SET column2= ' + column1 + ' WHERE yourTableID = '+CAST(yourTableID AS VARCHAR(3))
FROM yourTable
PRINT @SQL
EXEC(@SQL)
--Check results
SELECT * FROM yourTable
ROLLBACK
January 10, 2012 at 8:24 am
Nice!
If you haven't even tried to resolve your issue, please don't expect the hard-working volunteers here to waste their time providing links to answers which you could easily have found yourself.
January 10, 2012 at 11:31 am
This is working but I am looking soothing like a scaler function that can be used in Select statement. Any idea?
select ..., dbo.fnExpressionToValue(Expr)
from myTable
January 11, 2012 at 2:19 am
kausmail (1/10/2012)
This is working but I am looking soothing like a scaler function that can be used in Select statement. Any idea?select ..., dbo.fnExpressionToValue(Expr)
from myTable
That's a different requirement to the one you originally stated.
In this case, you'd have to use a CLR as you can't execute a string in a function. If you need help writing one (and someone else doesn't post one in between), I'll knock up a simple one later on today.
January 12, 2012 at 3:03 am
Cadavre (1/11/2012)
In this case, you'd have to use a CLR as you can't execute a string in a function. If you need help writing one (and someone else doesn't post one in between), I'll knock up a simple one later on today.
Well, running a little late obviously 😀
Nice and simple CLR, I've not exactly thoroughly tested this so you'll want to do lots of tests first.
using System;
using System.Data;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;
namespace executeString
{
public class UserDefinedFunctions
{
[SqlFunction]
public static SqlString ExecuteString(SqlString maths)
{
var mathString = maths.ToString().Replace(" ", "");
string mathResult;
try
{
var result = new DataTable().Compute(mathString, null);
mathResult = result.ToString();
}
catch (Exception)
{
mathResult = null;
}
mathResult = string.IsNullOrEmpty(mathResult) ? null : mathResult;
return new SqlString(mathResult);
}
};
}
BEGIN TRAN
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[ExecuteString]') AND type in (N'FN', N'IF', N'TF', N'FS', N'FT'))
DROP FUNCTION [dbo].[ExecuteString]
IF EXISTS (SELECT * FROM sys.assemblies asms WHERE asms.name = N'executeString' and is_user_defined = 1)
DROP ASSEMBLY [executeString]
GO
CREATE ASSEMBLY [executeString]
AUTHORIZATION [dbo]
FROM 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WITH PERMISSION_SET = SAFE
GO
CREATE FUNCTION [dbo].[ExecuteString](@maths [nvarchar](4000))
RETURNS [nvarchar](4000) WITH EXECUTE AS CALLER
AS
EXTERNAL NAME [executeString].[executeString.UserDefinedFunctions].[ExecuteString]
GO
CREATE TABLE yourTable (yourTableID INT IDENTITY, column1 VARCHAR(500), column2 VARCHAR(500))
INSERT INTO yourTable (column1)
SELECT '2 * 2+1 * 7'
UNION ALL SELECT '1 * 1+2 * 4'
UNION ALL SELECT '1 * 1+2 * 4+1 * 4'
SELECT column1, [dbo].[ExecuteString] (column1)
FROM yourTable
ROLLBACK
Which will return: -
column1
------------------- --------------------
2 * 2+1 * 7 11
1 * 1+2 * 4 9
1 * 1+2 * 4+1 * 4 13
Since you never replied to my last message, I'm assuming that a CLR is an option for you?
Viewing 7 posts - 1 through 6 (of 6 total)
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