PL/SQL For Practitioners – #5 Procedures

Hi folks,

A procedure is a subprogram that performs a specific action. This feature is extremely important and vastly that we can use when developing in PL/SQL. Before invoking a procedure, you must declare and define it. You can either declare it first (with procedure_declaration) and then define it later in the same block, subprogram, or package (with procedure_definition) or declare and define it at the same time (with procedure_definition).

Syntax

create or replace procedure <Name> (<parameter list>)
as 
  --local variable declaration
begin
   --code section
exceptions --optional
  --handlers
end;

Example 1

The following procedure is a quite simple example and it is responsible for inserting new registers to the log table. The file create_table_it_tutorial_log create_table_it_tutorial_log

Procedure

CREATE OR REPLACE
PROCEDURE p_insert_log (p_descr_log varchar2) AS

   v_new_id number;
   
BEGIN
  
  select nvl(max(id), 0) + 1 into v_new_id from it_tutorial_log;
  
  insert into it_tutorial_log (id, descr_log, date_log, user_log) values (v_new_id, p_descr_log, sysdate, user);
  
END p_insert_log;

Execution

DECLARE
  P_DESCR_LOG VARCHAR2(200);
BEGIN
  
  P_DESCR_LOG := 'FIRST PROCEDURE TEST';

  P_INSERT_LOG( P_DESCR_LOG );
  
END;

Example 2 – Adding exception handling

For more details about exception handling please check out my post below

PL/SQL For Practitioners – #4 Exception Handling

Procedure

create or replace
PROCEDURE p_insert_log (p_descr_log varchar2,
                        p_msg_return OUT varchar2) AS

   v_new_id NUMBER;
   v_local_except EXCEPTION;
   v_error_msg VARCHAR2(255);
   
   
BEGIN
  
  select nvl(max(id), 0) + 1 into v_new_id from it_tutorial_log;
  
  IF NVL(p_descr_log, 'N') = 'N' THEN
     v_error_msg := 'The description is a required column!';
     raise v_local_except;
  END IF;
     
  insert into it_tutorial_log (id, descr_log, date_log, user_log) values (v_new_id, p_descr_log, sysdate, user);

EXCEPTION
   WHEN v_local_except THEN
       p_msg_return := 'Program: p_insert_log - Error: ' || v_error_msg;
  
END p_insert_log;

Execution

DECLARE
   P_DESCR_LOG VARCHAR2(255);
   P_OUTPUT VARCHAR2(255);
BEGIN
   P_DESCR_LOG := null;
   P_INSERT_LOG( P_DESCR_LOG, P_OUTPUT);

   IF NVL(P_OUTPUT, 'N') != 'N' THEN
      dbms_output.put_line(P_OUTPUT);
   END IF;
END;

This post is part of a series about the most common structures in PL/SQL. You can check the rest of them in the link below.

PL/SQL for real world – 8 features that you have to know

Please write down in the comments any further questions you may have. I’ll be happy to help you.

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