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Varchar Operator to Dynamic Formula

Posted on 2013-02-04
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Last Modified: 2013-02-04
Hi Experts

I have a requirement for a user to enter two  numbers into a db and an operator, TSQL would do its magic and then return a result. I have the code below, but the problem  is that the operator is a varchar and building the formula is converting the output to a string - I need it to process the formula. Im thinking of sort sort of dyanamic SQL.

Below is my test code example - expected result is 200.

create TABLE  ##TEST
(
VALUE1 NUMERIC,
OPERATOR VARCHAR,
VALUE2 NUMERIC

)

INSERT INTO ##TEST VALUES ('100','+','100')


SELECT CONVERT(VARCHAR,VALUE1) + ' ' + OPERATOR + ' ' +  CONVERT(VARCHAR,VALUE2) FROM
(SELECT VALUE1, CASE OPERATOR
                                     WHEN '+' THEN '+'
                                    ELSE '-'
END AS OPERATOR, VALUE2 FROM ##TEST) AS A




DROP TABLE ##TEST
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Question by:MrDavidThorn
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3 Comments
 
LVL 23

Accepted Solution

by:
Ioannis Paraskevopoulos earned 500 total points
ID: 38850363
Hi,

Please se the following:

create TABLE  ##TEST
(
VALUE1 NUMERIC,
OPERATOR VARCHAR,
VALUE2 NUMERIC

)

INSERT INTO ##TEST VALUES ('100','+','100')

DECLARE @SQL AS VARCHAR(500)--Here you probably want to change that. You need to consider how big are the numbers you are expecting

SET @SQL = 'SELECT ' + (
SELECT CONVERT(VARCHAR,VALUE1) + ' ' + OPERATOR + ' ' +  CONVERT(VARCHAR,VALUE2) FROM
(SELECT VALUE1, CASE OPERATOR 
                                     WHEN '+' THEN '+'
                                    ELSE '-' 
END AS OPERATOR, VALUE2 FROM ##TEST) AS A ) 

EXEC(@SQL)



DROP TABLE ##TEST

Open in new window


Giannis
0
 

Author Comment

by:MrDavidThorn
ID: 38850364
I have worked out this way - only problem is that I can only hand one row at time, is there a way I can handle a record set.



create TABLE  ##TEST
(
VALUE1 NUMERIC,
OPERATOR VARCHAR,
VALUE2 NUMERIC

)

DECLARE @FORMULA varchar(max)

INSERT INTO ##TEST VALUES ('100','+','100')


SELECT @FORMULA =  (CONVERT(VARCHAR,VALUE1) + ' ' + OPERATOR + ' ' +  CONVERT(VARCHAR,VALUE2))  FROM
(SELECT VALUE1, CASE OPERATOR
                   WHEN '+' THEN '+'
                   ELSE '-'
END AS OPERATOR, VALUE2 FROM ##TEST) AS A

exec ('Select ' +  @FORMULA )


DROP TABLE ##TEST
0
 
LVL 23

Expert Comment

by:Ioannis Paraskevopoulos
ID: 38850373
You may use a cursor. Tell me if you need an example of how to do that.

To be more precise you should provide some sample data in order to figure out what input and what outpt you expect.
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