RE: Dynamic SQL: where do you draw the line?

Thomas Jeff Wed, 25 Jun 2003 11:53:12 -0700

Title: RE: Dynamic SQL: where do you draw the line?

Raj,

I'm aware of the table technique for converting inlists and employed that a few weeks ago in a

different stored procedure. I was thinking if we could make the DELETE static, then it could

soemthing look like this:

DELETE FROM TABLE
WHERE ASSET_GUID IN (SELECT * FROM THE (SELECT CAST( str2tab(p_str) as STRTABTYPE ) FROM DUAL))

AND SITE_GUIDE = p_site_guid

AND OBJECT_GUID = p_object_guid;

And I would have them code 7 small procedures each with the similar DELETE syntax. This way, with

static SQL, you eliminate both the hard and soft parsing. With EXEC IMMEDIATE, you will always at least

get the soft parsing. That's my understanding.

-----Original Message-----
From: Jamadagni, Rajendra [mailto:[EMAIL PROTECTED]
Sent: Wednesday, June 25, 2003 12:35 PM
To: Multiple recipients of list ORACLE-L
Subject: RE: Dynamic SQL: where do you draw the line?

Thomas,

IMHO You probably picked up a BAD example to make your point. Yes I agree with you, but here the table is unknown, which would make this a Dynamic_sql of type 4 or 3?). in this case you are constructing whole statement dynamically.

Also it seems user developers are sending a string of numbers separated by space, which is replaced by semicolon to make a dynamic IN List. This might be the weekenss, Send them a URL to Asktom site and show them how to convert inlists into a table for max flexibility in the code.

You could, OTOH run some quick tests on this code and another where you have one delete statement per table and use 10046 event to show them what impact it has on the database. I hate long if-then-else structures too.

ps: if you want to break this code, send in p_site_guid value as '1,2' and watch the fun. In case of dynamic sql like this (and especially if it is coming from web), have your developers learn about sql-injecting techniques ... you _must_ validate input against a KNOWN set of values before using them. You _must_ also reject all unknowns with appropriate feedback.

Raj
--------------------------------------------------------------------------------
Rajendra dot Jamadagni at nospamespn dot com
All Views expressed in this email are strictly personal.
QOTD: Any clod can have facts, having an opinion is an art !

-----Original Message-----
Sent: Wednesday, June 25, 2003 10:05 AM
To: Multiple recipients of list ORACLE-L

I've been fighting an ongoing war with our ecommerce developers, who are
inordinately fond of writing
dynamic SQL code that neglects to incorporate bind variables. Researching
AskTom I've
found and utilized different techniques to force bind variables into these
dynamic SQL queries,
including the use of application contexts, object types, etc.

However, I'm wondering if I'm making things worse, essentially providing
them with band-aids, when I should
be forcing them to change the way they code.

Consider the sample code below (which is a relatively simple example), which
is a generic DELETE statement
generator.

In this situation, the programmers claim the following code is good
programming practice, promotes
ease of maintenance, less buggy, and promotes code reusability (their
definition of reusability is a bit
different from mine).

I disagreed with them -- not only is this code not reusable at all, with the
parsing overhead consequences,
it's also harder to debug and tune for performance, due to all the
permutations that needs to be tested.
My take was that they be far better off writing a simple static DELETE
statement for each table.

Their rejoinder -- it's not worth writing lots of redundant code at the
expense of 'minimal' gains in
performance. Now, this code *could* be rewritten to use the SYS_CONTEXT
function on the p_object_id
and p_site_guid to force a bind variable on those two conditions, but the IN
condition with respect to the
p_asset_guid would be more problematic. However, I don't feel we should
have to be resorting to such measures
to get this code to using bind variables.

So, I'm at the point of denying such code to be migrated to production. I
recognize that there
are situations where there is a legitimate need for dynamic SQL, but the SQL
has to be written w/o catenating
literal SQL -- and if it can't -- they need to go back to square one.

Opinions? I'm curious -- do you have policies/standards with respect to
dynamic SQL?

CREATE OR REPLACE PROCEDURE test
(
    p_Asset_Guid        IN VARCHAR2,
    p_Object_Id         IN VARCHAR2,
    p_Object_Definition IN VARCHAR2,
    p_Site_Guid         IN VARCHAR2,
    p_result            IN OUT VARCHAR2

) AS

   strTableName VARCHAR2(100);
   strWhere VARCHAR2(100);
   strQuery LONG;

BEGIN
   IF p_Object_Definition = 'PRODUCT'
   THEN
       strTableName := ' TNE.GPD_PRODUCT_ASSET ';
       strWhere := ' MODEL_NO ';
   ELSIF p_Object_Definition = 'CARACTERISTIC'
        OR p_Object_Definition = 'CHARACTERISTIC'
   THEN
       strTableName := ' TNE.GPD_CARACTERISTIC_ASSET ';
       strWhere := ' CARACTERISTIC_ID ';
   ELSIF p_Object_Definition = 'CATEGORY'
   THEN
       strTableName := ' TNE.GPD_CATEGORY_ASSET ';
       strWhere := ' CATEGORY_GUID ';
   ELSIF p_Object_Definition = 'VALUE'
   THEN
       strTableName := ' TNE.GPD_VALUE_ASSET ';
       strWhere := ' VALUE_ID ';
   ELSIF p_Object_Definition = 'PRODUCT_NODE'
   THEN
       strTableName := ' TNE.GPD_PRODUCT_NODE_ASSET ';
       strWhere := ' PRODUCT_NODE_GUID ';
   ELSIF p_Object_Definition = 'CARAC_GROUP'
   THEN
       strTableName := ' TNE.GPD_CARAC_GROUP_ASSET ';
       strWhere := ' CARAC_GROUP_GUID ';
   END IF;

   strQuery := ' DELETE FROM ' || strTableName ||
               ' WHERE ASSET_GUID IN ( ''' || REPLACE(p_Asset_Guid,' ',
''',''') ||
               ''' ) AND ';

strQuery := strQuery || strWhere || ' = ''' || p_Object_Id || '''';
strQuery := strQuery || ' AND SITE_GUID = ''' || p_Site_Guid || '''';

execute immediate strQuery;

p_result := '1';

RETURN;
END;

--------------------------------------------
Jeffery D Thomas
DBA
Thomson Information Services
Thomson, Inc.

Email: [EMAIL PROTECTED]

Indy DBA Master Documentation available at:
http://gkmqp.tce.com/tis_dba
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RE: Dynamic SQL: where do you draw the line?

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