Pragma EXECPTION_INIT and its usage ?

The PRAGMA EXECPTION_INIT tells the complier to associate an exception with an oracle error. To get an error message of a specific oracle error.

 

     e.g. PRAGMA EXCEPTION_INIT (exception name, oracle error number)

 

Pragma exception_init Allow you to handle the Oracle predefined message by you'r own message. means you can instruct compiler toassociatethe specific message to oracle predefined message at compile time.This way you Improve the Readbility of your program and handle it accoding to your own way.
It should be declare at the DECLARE section.
example
declare
salary number;
FOUND_NOTHING exception;
Pragma exception_init(FOUND_NOTHING 100);
begin
select sal in to salaryfrom emp where ename ='ANURAG';
dbms_output.put_line(salary);
exception
WHEN FOUND_NOTHING THEN
dbms_output.put_line(SQLERRM);
end;

difference between explicit cursor and implicit cursor in oracle

When a single insert, delete or update statement is executed within PL/SQL program then oracle creates an implicit cursor for the same, executes the statement, and closes the cursor. You can check the result of execution using SQL%ROWCOUNT function.

Explicit cursors are created programmatically. The cursor type variable is declared and associated with SQL query. The program then opens a cursor, fetches column information into variables or record type variable, and closes cursor after all records are fetched. To check whether cursor is open or not use function SQL%ISOPEN and to check whether there are any records to be fetched from the cursor use function SQL%FOUND.