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SQL Server Eval Equivalent

Author

Topic

pah4mpo
Starting Member

2 Posts

Posted - 2005-05-04 : 11:35:09

I have a script which returns a mathematical string i.e “10 + 10 “ I need a way in which to evaluate this string within an SQL Server stored procedure. I have provided some pseudo code to help illustrate my point.

Declare @income as string
SET @Income = ’10 + 10’

Set @output = eval( @income )

Print @Output.

Incoimg string is equal to : “10+10”

We need the result to return 20 ie

Eval(‘10+10’) = 20

NOT "1010" etc

Thanks in advance for your help

Paul

tkizer
Almighty SQL Goddess

38200 Posts

Posted - 2005-05-04 : 15:21:37

You shouldn't be doing this inside your stored procedure. Why do you have this requirement for the stored procedure instead of from your application?

Tara

X002548
Not Just a Number

15586 Posts

Posted - 2005-05-04 : 15:34:21

Well, that's a new one....

You would have to worry about the rules of opertaional applications (there's a real for it I forget) but for example operators get applied in an order I belive...like mult, the dicision , then addition the substraction.

Plus you'd have to worry about parathesis...and would about roots and powers..or to get crazy trig functions?

Where does EVAL come from Oracle?

Brett

8-)

EDIT:

You would have to head down this road...most likely using a function


DECLARE @expr varchar(8000)
SELECT @expr = '10+10'
SELECT    CONVERT(int,
	  SUBSTRING(@expr,1,CHARINDEX('+',@expr)-1))
	+ CONVERT(int,
	  SUBSTRING(@expr
	, CHARINDEX('+',@expr)+1
	, LEN(@expr)-CHARINDEX('+',@expr)+1
	))

X002548
Not Just a Number

15586 Posts

Posted - 2005-05-04 : 15:54:13

Aww hell...another case of overthinking a problem


DECLARE @expr nvarchar(4000), @Result int
SELECT @expr = N'10+10'

SELECT @expr = N'SELECT @Result=' + @expr
execute sp_executesql 
          @expr,
          N'@Result int OUT', @Result OUT
SELECT @Result

Brett

8-)

tkizer
Almighty SQL Goddess

38200 Posts

Posted - 2005-05-04 : 15:59:38

And don't forget to run with scissors!

Tara

rockmoose
SQL Natt Alfen

3279 Posts

Posted - 2005-05-04 : 16:37:08

How about writing an extended stored procedure expression validator
here are some tips: [url]http://www.arstdesign.com/articles/expression_evaluation.html[/url]
on implementation.

I think I saw a sql version at sqlservecentral.com

Or ask the users to use calc.exe

rockmoose

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