1. Best Practices in PL/SQL
Karthikeyan M .

2. Why best practices? Many ways of writing a code Code Best code
Will give solution (some how)
Time taken and resource consumed ?
Best code
Use optimal resource
Provides quicker solution .

3. Spend more time in design
Modularized Design
Bad design
Dump your logic in a single procedure
Having lots of selects inserts updates and deletes….etc
Good design
Break your logic into small blocks
Grouping related logic as a single block or program
Spend more time in design
Less time in coding .

4. Modularize Modularize will Use Packages reduce complexity
make your tasks manageable
make your resulting code maintainable
Use Packages
For each major functionality
With repeated DML as procedure
With repeated select as functions .

5. Naming convention Follow a standard throughout your code Example
Easy to understand
Easy for maintain and change
Example
Local variable l_var_name
Procedure parameter p_var_name
Global variable g_var_name
Follow the standard throughout
your code and application .

6. Avoid hard coding As begin select d_no into an_document_number as
CREATE OR REPLACE PROCEDURE GEN_SWIP
( an_document_number IN number,
an_serv_item_id IN number,
an_srsi_ip_addr_seq IN varchar(20)) As
begin
select d_no into an_document_number
from task;
end;
CREATE OR REPLACE PROCEDURE GEN_SWIP
( an_document_number IN asap.serv_req_si.document_number%TYPE,
an_serv_item_id IN
asap.serv_req_si.serv_item_id%TYPE,
an_srsi_ip_addr_seq IN asap.srsi_ip_addr.srsi_ip_addr_seq%TYPE,) as
begin
null;
end;
What happens if the d_no column changed to varchar2 type ? .

7. Avoid SQL ! SQL is equivalent to hard-coding Encapsulate your SQL
Drag the performance down
Difficult to maintain
Encapsulate your SQL
Selects inside functions
DMLs inside procedures
And call these inside your business logic
We will see an example
for this later. .

8. Repeated SQL as functions
This is quintessential for performance
Avoid repeating the SQL in different places
Hard parsing will be avoided
Identify at the time of designing
So spend more time in design
rather than coding .

9. Exception handling A common package for Normally Error handling
Error logging
Log as more a data as possible (debugging)
Normally
Date of occurrence
Error number , name
Program name and program data…etc .

10. Use BULK COLLECT for Queries
CREATE OR REPLACE FUNCTION get_a_mess_o_emps
(deptno_in IN dept.depno%TYPE)
RETURN emplist_t IS
emplist emplist_t := emplist_t();
TYPE numTab IS TABLE OF NUMBER;
TYPE charTab IS TABLE OF VARCHAR2(12);
TYPE dateTab IS TABLE OF DATE;
enos numTab;
names charTab;
hdates dateTab;
BEGIN
SELECT empno, ename, hiredate
BULK COLLECT INTO enos, names, hdates
FROM emp
WHERE deptno = deptno_in;
emplist.EXTEND(enos.COUNT);
FOR i IN enos.FIRST..enos.LAST
LOOP
emplist(i) := emp_t(enos(i),
names(i), hiredates(i));
END LOOP;
RETURN emplist;
END;
BULK COLLECT performs bulk bind of results from SQL select statement
Returns each selected expression in a table of scalars .

11. Use the FORALL Statement
Instead of the individual FOR operations, you can do this:
Used to reduce the context switching between SQL and PL/SQL engine
PROCEDURE update_employee (p_name customer.name%TYPE) IS
BEGIN
FORALL cust_dt IN (select cust_name ,cust_id,cust_age from customer where cust_name= p_name )Loop
Begin
--bussiness logic
End;
END; .

12. Procedural statement executor SQL statement executor
Conventional Bind
Oracle server
PL/SQL Runtime Engine
SQL Engine
Procedural statement executor
PL/SQL block
SQL statement executor
FOR aDept IN deptlist.FIRST..
deptlist.LAST
LOOP
DELETE emp
WHERE deptno = deptlist(aDept);
END LOOP;
Performance penalty for many “context switches” .

13. Procedural statement executor SQL statement executor
Enter the “Bulk Bind”
Oracle server
PL/SQL Runtime Engine
SQL Engine
Procedural statement executor
PL/SQL block
SQL statement executor
FORALL aDept IN deptlist.FIRST..
deptlist.LAST
DELETE emp
WHERE deptno = deptlist(aDept);
Much less overhead for context switching .

14. Points to remember Take more time in designing Follow coding standard
Avoid hard coding
Avoid writing more SQL
Write tiny chunk of code
Don’t repeat anything .

15. Books/ Materials “Beginning Oracle Programming “
Sean Dillon, Christopher Beck , Thomas Kyte
“Code Complete” by Steve McConnell .