Best+Practices+in+PL SQL

7/27/2019 Best+Practices+in+PL SQL

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Why best practices?

Many ways of writing a code

Code

Will give solution (some how) Time taken and resource consumed ?

Best code Use optimal resource

Provides quicker solution


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Modularized Design

Bad design Dump your logic in a single procedure

Having lots of selects inserts updatesand deletes.etc

Good design Break your logic into small blocks

Grouping related logic as a single blockor program

Spend more time in designLess time in coding


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Modularize

Modularize will 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


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Naming convention

Follow a standard throughout yourcode 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 throughoutyour code and application


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Avoid hard coding

CREATEORREPLACEPROCEDURE 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 INasap.srsi_ip_addr.srsi_ip_addr_seq

%TYPE,)asbeginnull;end;

CREATEORREPLACEPROCEDURE GEN_SWIP( an_document_number IN number,an_serv_item_id IN number,

an_srsi_ip_addr_seq IN varchar(20))As

beginselect d_no into an_document_numberfrom task;

end;

What happens if the d_no column changed tovarchar2 type ?


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Avoid SQL !

SQL is equivalent to hard-coding 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 examplefor this later.


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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 designingSo spend more time in design

rather than coding


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Exception handling

A common package for Error handling Error logging Log as more a data as possible

(debugging)

Normally

Date of occurrence Error number , name Program name and program dataetc


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Use the FORALL Statement

Instead of the individual FOR operations,you can do this:

Used to reduce the context switchingbetween SQL and PL/SQL engine

PROCEDURE update_employee (p_name customer.name%TYPE)ISBEGINFORALL cust_dt IN (select cust_name,cust_id,cust_age from customer where cust_name=p_name )LoopBegin--bussiness logicEnd;END;


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Oracle server

PL/SQL Runtime Engine SQL Engine

PL/SQL blockProcedural

statement

executorSQL

statement

executor

FOR aDept IN deptlist.FIRST..deptlist.LAST

LOOPDELETE empWHERE deptno = deptlist(aDept);

END LOOP;

Performance penaltyPerformance penaltyfor many contextfor many context

switchesswitches

Conventional Bind


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Enter the Bulk Bind

Oracle server

PL/SQL Runtime Engine SQL Engine

PL/SQL blockProcedural

statement

executorSQL

statement

executor

FORALL aDept IN deptlist.FIRST..deptlist.LASTDELETE empWHERE deptno = deptlist(aDept);

Much less overheadMuch less overheadfor context switchingfor context switching


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Points to remember

Take more time in designing

Follow coding standard

Avoid hard coding Avoid writing more SQL

Write tiny chunk of code

Dont repeat anything


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Books/ Materials

Beginning Oracle Programming

Sean Dillon, Christopher Beck ,

Thomas Kyte http://asktom.oracle.com

http://www.toadworld.com/sf

Code Complete by Steve McConnell
http://asktom.oracle.com/http://www.toadworld.com/sfhttp://www.toadworld.com/sfhttp://www.toadworld.com/sfhttp://asktom.oracle.com/

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Best+Practices+in+PL SQL