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 Variables in Where Clause
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SyDiko
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22 Posts

Posted - 08/20/2013 :  14:54:49  Show Profile  Reply with Quote
Hi Guys,

I need some help with my SQL logic, and I've been working (and researching) this all day with zero success... So I turn to the gurus! :)

My goal is to try an pass a variable from an ASP page to a stored procedure, which is utilizing the variable as criteria for a column_name in the where clause.

So for example (a simplified version of my query):

@strDept nvarchar(10), @strUser nvarchar(30)
-- the asp page will pass f19 to @strDept
-- the asp page will pass the logged in username to @strUser

select x, y, z from table1 where @strDept in (@strUser)

Now my question is: Is this at all possible? The stored procedure does execute, but it returns no values. Is that because the where variable has no data at compile time? If not, I can't think of any reason why this is not working.

Can anyone recommend a better way to do this? (I have tried a case statement, before the select to set the variable too and that returned the same result.)

(Thank you for taking the time to read my post by the way.)

Edited by - SyDiko on 08/20/2013 14:58:50

Lamprey
Flowing Fount of Yak Knowledge

4614 Posts

Posted - 08/20/2013 :  15:55:56  Show Profile  Reply with Quote
You can do a lot of "interesting" things with Dynamic SQL. I'm not sure I follow the logic, but here is a very unsafe query:
EXEC ('select x, y, z from table1 where ' + @strDept + ' in (' + CHAR(39) + @strUser + CHAR(39) + ')'
My question is, why would you pass in the column name? Wouldn't you already know what it is? Perhaps, there is no need for dynamic sql at all and you can just pass the User to a stored procedure?

Here is a link that has lots of info on dynamic sql:
http://www.sommarskog.se/dynamic_sql.html


Edited by - Lamprey on 08/20/2013 16:01:49
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SwePeso
Patron Saint of Lost Yaks

Sweden
30242 Posts

Posted - 08/20/2013 :  16:26:41  Show Profile  Visit SwePeso's Homepage  Reply with Quote
Perhaps a warning against SQL injection is is proper?
DECLARE	@SQL NVARCHAR(MAX);

SET	@SQL = 'SELECT x, y, z FROM dbo.Table1 WHERE ' + QUOTENAME(@strDept) + ' IN (' + QUOETNAME(@strUser, '''') + ');';
EXEC	(@SQL);



Microsoft SQL Server MVP, MCT, MCSE, MCSA, MCP, MCITP, MCTS, MCDBA
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SyDiko
Starting Member

22 Posts

Posted - 08/20/2013 :  16:28:29  Show Profile  Reply with Quote
quote:
Originally posted by Lamprey

You can do a lot of "interesting" things with Dynamic SQL. I'm not sure I follow the logic, but here is a very unsafe query:
EXEC ('select x, y, z from table1 where ' + @strDept + ' in (' + CHAR(39) + @strUser + CHAR(39) + ')'




Oh wow, didn't know you could do that - I will try and apply to my where clause.

quote:
Originally posted by Lamprey
My question is, why would you pass in the column name? Wouldn't you already know what it is? Perhaps, there is no need for dynamic sql at all and you can just pass the User to a stored procedure?



Well, that's the thing - technically I'm writing the stored procedure as a query and the results are going to be displayed on 2 types of pages. The first page is a manager view, and this page will display all the data listed in the criteria. The second report is an individual view per department, which is modeled by my example above. The problem is that each department has their own field name where the user's full name is stored, and in order to write less code, I figured a dynamic field name passed into the sp based on the asp variable would solve that. So for example, the sales field would be field1, and the processor is field2. Instead of writing 2 if statements to handle that, why not use dynamic sql to pass that info from the page to the sp?

I'm somewhat familiar with sql injection too, and I don't think it applies here, because the page is passing 2 static parameters and the user doesn't know anything about it. The page passes a 0 or 1 for the page view (individual or manager) and also the fieldid for the person's name) so they can see their own data. They are basically dashboards, (if that makes sense.)




(and thank you for the resource, I will take a look.)

Edited by - SyDiko on 08/20/2013 17:21:58
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SwePeso
Patron Saint of Lost Yaks

Sweden
30242 Posts

Posted - 08/20/2013 :  18:39:10  Show Profile  Visit SwePeso's Homepage  Reply with Quote
Never underestimate the stupidity, or geniality, of users.
If there is a crack in your system, someone will find it soon or enough and exploit it.




Microsoft SQL Server MVP, MCT, MCSE, MCSA, MCP, MCITP, MCTS, MCDBA
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SyDiko
Starting Member

22 Posts

Posted - 08/21/2013 :  09:53:56  Show Profile  Reply with Quote
Erm, still no luck with the above code and/or in the dynamic article.

Any other suggestions?

quote:
Originally posted by SwePeso

Never underestimate the stupidity, or geniality, of users.
If there is a crack in your system, someone will find it soon or enough and exploit it.




Microsoft SQL Server MVP, MCT, MCSE, MCSA, MCP, MCITP, MCTS, MCDBA



True that.
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James K
Flowing Fount of Yak Knowledge

3653 Posts

Posted - 08/21/2013 :  10:03:55  Show Profile  Reply with Quote
quote:
Originally posted by SyDiko

Erm, still no luck with the above code and/or in the dynamic article.

Any other suggestions?

quote:
Originally posted by SwePeso

Never underestimate the stupidity, or geniality, of users.
If there is a crack in your system, someone will find it soon or enough and exploit it.




Microsoft SQL Server MVP, MCT, MCSE, MCSA, MCP, MCITP, MCTS, MCDBA



True that.

Swepeso's code works correctly in my tests - see below. Can you post your code that does not work, or follow this example and see what you are doing differently?

CREATE TABLE #Table1 (x INT, y INT, z INT, f19 VARCHAR(32), f20 VARCHAR(32));
INSERT INTO #Table1 VALUES (1,2,3,'Smith',NULL);
INSERT INTO #Table1 VALUES (7,8,9,NULL,'Jones');
GO
-- Look in column f19.
DECLARE	@SQL NVARCHAR(MAX);
DECLARE @strDept VARCHAR(32) = 'f19';
DECLARE @strUser VARCHAR(32) = 'Smith';

SET	@SQL = 'SELECT x, y, z FROM #Table1 WHERE ' + QUOTENAME(@strDept) + ' IN (' + QUOTENAME(@strUser, '''') + ');';
EXEC	(@SQL);
GO
-- Look in column f20.
DECLARE	@SQL NVARCHAR(MAX);
DECLARE @strDept VARCHAR(32) = 'f20';
DECLARE @strUser VARCHAR(32) = 'Jones';

SET	@SQL = 'SELECT x, y, z FROM #Table1 WHERE ' + QUOTENAME(@strDept) + ' IN (' + QUOTENAME(@strUser, '''') + ');';
EXEC	(@SQL);
GO

DROP TABLE #Table1;
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Lamprey
Flowing Fount of Yak Knowledge

4614 Posts

Posted - 08/21/2013 :  10:41:08  Show Profile  Reply with Quote
I have to ask: is ther any chance you can fix your data structure? It seems very odd to have a column for each department. My guess is that it should be normalized so that you have a column for department(ID) and column for the Users Name. That would avoid the situation you are trying to find a solution for.
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SyDiko
Starting Member

22 Posts

Posted - 08/21/2013 :  14:02:04  Show Profile  Reply with Quote
Lamprey, I'm unable to edit the database - it was created by another company that works with their own software system. I'm merely querying the data via a custom view.

quote:
Originally posted by James K
Swepeso's code works correctly in my tests - see below. Can you post your code that does not work, or follow this example and see what you are doing differently?




I'll post the exact stored procedure..

quote:


ALTER PROCEDURE [dbo].[poli_platform_appraisalOrdered] @strDept nvarchar(50), @strUser nvarchar(50), @strDash nvarchar(1)
AS
set nocount on

-- Processing View
IF @strDash = '0'
Begin
select	
		f1 as 'Filename',
		f101 as 'Last Name',
		f18 as 'Credit Processor',

from all_fields where

		foldername in ('active')
		and f6315 not in ('1/1/2000')
		and datediff(d,f6315,getdate()) >= 6
		and f6316 is null
		and f1 not like '%lock%'
		and f1 not like '%NLNF%'
		and f1 not like '%NFNL%'
		and f1 not like '%register%'

	and '@strDept' = @strUser -- this is the problem portion!
			
order by datediff(d,f6020,getdate())
End

-- MGR View
if @strDash = '1'
Begin
select	
		f1 as 'Filename',
		f101 as 'Last Name',
		f18 as 'Credit Processor',

from all_fields where

		foldername in ('active')
		and f6315 not in ('1/1/2000')
		and datediff(d,f6315,getdate()) >= 6
		and f6316 is null
		and f1 not like '%lock%'
		and f1 not like '%NLNF%'
		and f1 not like '%NFNL%'
		and f1 not like '%register%'
			
order by datediff(d,f6020,getdate())
End




As you can see it's pretty ugly for a stored procedure, but thats how the asp pages were originally designed. They stuck the queries right into the procedure and the page calls them. The individual view is what is giving me problems.

Additionally, I didn't write the logic behind the asp page, rather I work with and around it where need be. I'm the only in-house dev at my company and much of this is self-taught over the last few years. I haven't had a formal SQL class yet, so please forgive my lack of best practice.

Edited by - SyDiko on 08/21/2013 14:17:04
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Lamprey
Flowing Fount of Yak Knowledge

4614 Posts

Posted - 08/21/2013 :  15:20:31  Show Profile  Reply with Quote
Yikes! :)

Anyway, I did a translation of the first query to D-SQL as a sample:
DECLARE @strDept nvarchar(50) = 'DeptName'
DECLARE @strUser nvarchar(50) = 'UserString'
DECLARE @Sql NVARCHAR(MAX);

SET @Sql = ''
SET @Sql = @Sql + 'select '
SET @Sql = @Sql + '		f1 as Filename,'
SET @Sql = @Sql + '		f101 as [Last Name],'
SET @Sql = @Sql + '		f18 as [Credit Processor],'
SET @Sql = @Sql + 'from '
SET @Sql = @Sql + '		all_fields '
SET @Sql = @Sql + 'where '
SET @Sql = @Sql + '		foldername in (' + CHAR(39) + 'active' + CHAR(39) + ') '
SET @Sql = @Sql + '		and f6315 not in (' + CHAR(39) + '1/1/2000' + CHAR(39) + ') '
SET @Sql = @Sql + '		and datediff(d,f6315,getdate()) >= 6 '
SET @Sql = @Sql + '		and f6316 is null '
SET @Sql = @Sql + '		and f1 not like ' + CHAR(39) + '%lock%' + CHAR(39)
SET @Sql = @Sql + '		and f1 not like ' + CHAR(39) + '%NLNF%' + CHAR(39) 
SET @Sql = @Sql + '		and f1 not like ' + CHAR(39) + '%NFNL%' + CHAR(39)
SET @Sql = @Sql + '		and f1 not like ' + CHAR(39) + '%register%' + CHAR(39)
SET @Sql = @Sql + '		and ' + QUOTENAME(@strDept) + ' = ' + QUOTENAME(@strUser, CHAR(39))
SET @Sql = @Sql + '	order by datediff(d,f6020,getdate())  '


SELECT @Sql

Edited by - Lamprey on 08/21/2013 15:30:58
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Lamprey
Flowing Fount of Yak Knowledge

4614 Posts

Posted - 08/21/2013 :  15:22:24  Show Profile  Reply with Quote
Forgot to mention, change the "SELECT @Sql" To "EXEC @Sql" to execute the query.
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Lamprey
Flowing Fount of Yak Knowledge

4614 Posts

Posted - 08/21/2013 :  15:29:48  Show Profile  Reply with Quote
Not sure if you care since that query is going to table scan anyway, but you can replace
order by datediff(d,f6020,getdate())
with
ORDER BY f6020 DESC
That avoid applying a function to the column.

Edited by - Lamprey on 08/21/2013 15:32:01
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SyDiko
Starting Member

22 Posts

Posted - 08/21/2013 :  15:41:14  Show Profile  Reply with Quote
Hm.. interesting piece of code.

I do have a few questions if that's okay.

I guess my first is, what is the difference between D-SQl and T-SQL?




Edited by - SyDiko on 08/21/2013 16:08:45
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Lamprey
Flowing Fount of Yak Knowledge

4614 Posts

Posted - 08/21/2013 :  15:47:03  Show Profile  Reply with Quote
quote:
Originally posted by SyDiko

Hm.. interesting piece of code - I will try as soon as I can and report back. :)

Additionally, what is the difference between D-SQl and T-SQL?

I use D-SQL and short hand for Dynamic-SQL.

Edited by - Lamprey on 08/21/2013 15:47:46
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SyDiko
Starting Member

22 Posts

Posted - 08/21/2013 :  16:09:52  Show Profile  Reply with Quote
quote:
Originally posted by Lamprey

quote:
Originally posted by SyDiko

Hm.. interesting piece of code - I will try as soon as I can and report back. :)

Additionally, what is the difference between D-SQl and T-SQL?

I use D-SQL and short hand for Dynamic-SQL.



Gotcha! :)

Okay one more question... What is the purpose of using the char data type to concatenate around the string? And, what exactly is it doing?

SET @Sql = @Sql + ' foldername in (' + CHAR(39) + 'active' + CHAR(39) + ') '
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James K
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3653 Posts

Posted - 08/21/2013 :  16:19:57  Show Profile  Reply with Quote
CHAR(39) is the single quote character. Since string literals in SQL Server are defined using single quotes, if your string literal itself includes a single quote, that becomes a problem. You can escape a single quote using another single quote - so for example like this:
SET @Sql = @Sql + '		foldername in (''active'') '
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SyDiko
Starting Member

22 Posts

Posted - 08/21/2013 :  16:51:15  Show Profile  Reply with Quote
quote:
Originally posted by James K

CHAR(39) is the single quote character. Since string literals in SQL Server are defined using single quotes, if your string literal itself includes a single quote, that becomes a problem. You can escape a single quote using another single quote - so for example like this:
SET @Sql = @Sql + '		foldername in (''active'') '




Gotcha, and obviously foldername in(''active'') (which is implicit) will return a syntax error. By explicitly using the char, you avoid that syntax error?
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James K
Flowing Fount of Yak Knowledge

3653 Posts

Posted - 08/21/2013 :  17:04:47  Show Profile  Reply with Quote
No, that is not what I meant. If you run the entire query that Lamprey posted, and then run the same query, except replace that single line with what I posted, you will see that they give the same output. So you can use CHAR(39) or double up on the quotes to escape.

-- replace this line in Lamprey's code 
SET @Sql = @Sql + '		foldername in (' + CHAR(39) + 'active' + CHAR(39) + ') '
-- with this line and you should get the same results.
SET @Sql = @Sql + '		foldername in (''active'') '


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SyDiko
Starting Member

22 Posts

Posted - 08/21/2013 :  17:30:37  Show Profile  Reply with Quote
quote:
Originally posted by James K

No, that is not what I meant. If you run the entire query that Lamprey posted, and then run the same query, except replace that single line with what I posted, you will see that they give the same output. So you can use CHAR(39) or double up on the quotes to escape.

-- replace this line in Lamprey's code 
SET @Sql = @Sql + '		foldername in (' + CHAR(39) + 'active' + CHAR(39) + ') '
-- with this line and you should get the same results.
SET @Sql = @Sql + '		foldername in (''active'') '






Oooh, okay - kind of see what you mean!

I haven't had a chance to implement... I will try it in the morning when I'm back at work. :)
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SyDiko
Starting Member

22 Posts

Posted - 08/22/2013 :  17:08:06  Show Profile  Reply with Quote
My apologies for a double-post, but I just wanted to reply back with a success!

However, I wasn't able to do the above code, because my predecessor designed the .asp pages to use some funky functions on the front-end when the stored procedure executes. I think that is why I was having trouble with the above - I figured it out earlier this morning because it would work when I execute the procedure from SSMS, but not on the page.

After punching a few holes in a wall, an idea came to me. What I simply did was used this at the end of the original query:

@strUser In (f18,f19,f20,f21, so on and so forth)

this simple piece of code, just saved me hours of work lol. I just pass the username to the IN statement and make the procedure check each name field until it finds a match. This successfully accomplished exactly what I was looking to do!

Its not pretty, but it gets the job done.

Thanks everyone for your help, if it wasn't for you guys - I'd still be trying to figure this out.


Edited by - SyDiko on 08/22/2013 17:13:21
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