Parameters-Procedure and Function in PL/SQL

Index - PL/SQL Tutorial

Introduction to PL/SQL
Chap 1 : Block structure and Advantages of PL/SQL
Chap 2 : PL/SQL Variables and Constants
Chap 3 : PL/SQL Records
Chap 4 : PL/SQL IF ELSE statement / Conditional statements
Chap 5 : PL/SQL FOR and WHILE LOOP / Iterative Statements
Chap 6 : Cursors in PL/SQL
Chap 7 : PL/SQL Procedures
Chap 8 : PL/SQL Functions
Chap 9 : Parameters-Procedure and Function in PL/SQL
Chap 10 : What are PL/SQL Triggers
Chap 11 : Exception Handling in PL/SQL

How to pass parameters to Procedures and Functions in PL/SQL ?
In PL/SQL, we can pass parameters to procedures and functions in three ways.

1) IN type parameter: These types of parameters are used to send values to stored procedures.
2) OUT type parameter: These types of parameters are used to get values from stored procedures. This is similar to a return type in functions.
3) IN OUT parameter: These types of parameters are used to send values and get values from stored procedures.

Explanation :

1) IN parameter:
This is similar to passing parameters in programming languages. We can pass values to the stored procedure through these parameters or variables. This type of parameter is a read only parameter. We can assign the value of IN type parameter to a variable or use it in a query, but we cannot change its value inside the procedure.

The General syntax to pass a IN parameter is

CREATE [OR REPLACE] PROCEDURE procedure_name (
param_name1 IN datatype, param_name12 IN datatype ... )

param_name1, param_name2... are unique parameter names.
datatype - defines the datatype of the variable.

IN - is optional, by default it is a IN type parameter.

2) OUT Parameter:
The OUT parameters are used to send the OUTPUT from a procedure or a function. This is a write-only parameter i.e, we cannot pass values to OUT paramters while executing the stored procedure, but we can assign values to OUT parameter inside the stored procedure and the calling program can recieve this output value.

The General syntax to create an OUT parameter is

CREATE [OR REPLACE] PROCEDURE proc2 (param_name OUT datatype)

The parameter should be explicity declared as OUT parameter.

3) IN OUT Parameter:

The IN OUT parameter allows us to pass values into a procedure and get output values from the procedure. This parameter is used if the value of the IN parameter can be changed in the calling program.

By using IN OUT parameter we can pass values into a parameter and return a value to the calling program using the same parameter. But this is possible only if the value passed to the procedure and output value have a same datatype. This parameter is used if the value of the parameter will be changed in the procedure.

The General syntax to create an IN OUT parameter is

CREATE [OR REPLACE] PROCEDURE proc3 (param_name IN OUT datatype)

Example :

Using IN and OUT parameter:

Let’s create a procedure which gets the name of the employee when the employee id is passed.

CREATE OR REPLACE PROCEDURE emp_name (id IN NUMBER, emp_name OUT NUMBER)
IS
BEGIN
SELECT first_name INTO emp_name
FROM emp_tbl WHERE empID = id;
END;
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