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Dynamic SQL in stored procs

Posted on 2001-06-14
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Last Modified: 2008-02-26
Hi,


   I'm writing a stored proc to return a resultset on a Sybase DB. The complication is that one of
the parameters into the proc is a value which indicates which field on a table a second parameter belongs
to.

   E.G. Say MyTable has a number of fields, 3 of which are identifiers for a record, called Code1,
Code2, Code3. My proc will receive a first parameter with a value of 'LOG1' say. This is the value of
the key. A second parameterrepresents which Code type it belongs to, for example 'Code2'. This would
then mean a WHERE condition can be added to the SELECT statement saying

   WHERE MyTable.Code2 = @Parameter1

OR

   WHERE MyTable.Code2 = 'LOG1'

How would you implement something like this? Would you dynamically generate the SQL, or write a SELECT
for each possibility of 'Code' field and seperate them with an IF condition on @Parameter2. Or can you
embed an IF statement into a SELECT statement to say :

   IF @parameter2 = 'Code1'
       WHERE MyTable.Code1 = @parameter1
   ELSEIF @parameter2 = 'Code2'
       WHERE MyTable.Code2 = @parameter1
   ..
   ..

Help much appreciated...

Nik
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Question by:NikWhitfield
2 Comments
 
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Accepted Solution

by:
bret earned 0 total points
ID: 6192429
Hi Nik,  

You didn't specify *which* Sybase product you are writing for (ASA, ASE, ASIQ); I will assume ASE.

You can't imbed an if statement in the select as per your example.

Using dynamic sql is probably the easiest method if you are just trying to create a select statement,
but this is only available with ASE 12.0 and higher.  (from 11.5 up you can also hack the server to
be able to use sp_remotesql against the "local" server and accomplish much that same thing, but
the 12.0 EXECUTE solution is much cleaner).


declare @sqlstring varchar(255)
select @sqlstring = "select  * from mytable where "+@param2+ " = " + @param1
execute (@sqlstring).

See the "dynamicsql " section at http://www.sypron.nl for some additional pointers and examples.

-bret
0
 

Author Comment

by:NikWhitfield
ID: 6195497
Thanks Bret -

    I've actually redesigned things so dynamic SQL is not required. No doubt this will come in handly in the near future though...
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