Dynamic PL/SQL block vs dynamic SQL SELECT

Question

Hi there,
I have a question regarding the optimal way to code a dynamic SELECT INTO statement. Below are the 2 posiibilities I know of:
_1. Dynamically executing the SELECT statement and making use of the INTO clause of the EXECUTE IMMEDIATE statement_
CREATE OR REPLACE FUNCTION get_num_of_employees (p_loc VARCHAR2, p_job VARCHAR2)
RETURN NUMBER
IS
v_query_str VARCHAR2(1000);
v_num_of_employees NUMBER;
BEGIN
v_query_str := 'SELECT COUNT(*) FROM emp_'
|| p_loc
|| ' WHERE job = :bind_job';
EXECUTE IMMEDIATE v_query_str
INTO v_num_of_employees
USING p_job;
RETURN v_num_of_employees;
END;
_2. Encapsulating the SELECT INTO statement in a block and dynamically exectuting the block_
CREATE OR REPLACE FUNCTION get_num_of_employees (p_loc VARCHAR2, p_job VARCHAR2)
RETURN NUMBER
IS
v_query_str VARCHAR2(1000);
v_num_of_employees NUMBER;
BEGIN
v_query_str := 'begin
SELECT COUNT(*) INTO :into_bind FROM emp_'
|| p_loc
|| ' WHERE job = :bind_job;
end;';
EXECUTE IMMEDIATE v_query_str
USING out v_num_of_employees, p_job;
RETURN v_num_of_employees;
END;
I was just wondering which way would be preferred? I know the second method uses a bind variable for the INTO clause, but does the first one also use bind varialbes (no semi-colon)? Any differences in terms of efficiency or speed?
Thanks alot
Edited by: BYS2 on Oct 19, 2011 1:23 AM

Answer 1

sybrand_b wrote:
No difference in terms of performance or speed
Both variants will wreck the primary purpose of PL/SQL: to avoid parsing.
When I would see a 'developer' do this, I would fire him on the spot.
Why abuse PL/SQL in such a fashion? Both statements don't require parsing, as there is nothing dynamic in them and indicate a complete lack of understanding of Oracle, or a desire to deliver completely unscalable applications, resulting in end-users desiring to lynch you, and rightly so.
Remove the dynamic SQL or find another job.
Sybrand Bakker
Senior Oracle DBANot dynamic? What if p_loc and p_job were generated dynamically based on user-input? or what if there were potentially thousands of tables that p_loc could refer to? Should I make a CASE statement with a thousand cases?
In addition, the first example was actually taken directly from the official Oracle Database Application Developer's Guide (version 10.2). http://download.oracle.com/docs/cd/B19306_01/appdev.102/b14251/adfns_dynamic_sql.htm#i1006429 - look under 'Sample Single-Row Query Using Native Dynamic SQL' heading. Therefore, if you have any issues with this alleged 'improper' usage of dynamic SQL, perhaps you should go talk to Oracle directly.
While I appreciate your response, I don't think it has occurred that you that not everyone is a 'developer'. In fact, I have only very recently (several days ago) taught myself how to use Oracle SQL, PL/SQL and XMLDB by reading several of the official Oracle language and developer's guides. It is more a passing interest to me as I am working on some medical research which may require the use of a database. I am actually in medical school at the moment but have an undergraduate degree in Electrical and Computer engineering so I am generally well-versed in programming.
Perhaps the next time, you post your rubbish, rude and unhelpful comments, you should stop and think that people come to this forum because they need help and not because they want to be told to 'find another job'. In fact, I am quite certain that I could make you look absolutely stupid in any topic of electrical engineering or medicine.
Please do us all a favour and stop polluting this forum with your vapid posts. While I understand that your behavior is likely a compensatory mechanism to cope with your inferiority complex, know that help IS available if you need it.
Edited by: BYS2 on Oct 19, 2011 2:13 AM