DB2 is a popular database management system used by many organizations to store and manage their data. One of the key features of DB2 is the ability to create and execute stored procedures. These procedures are pre-compiled and stored in the database, making them faster to execute and more efficient.
When working with DB2 stored procedures, it is common to retrieve a return value from the procedure after it has been executed. In this article, we will explore the different methods for retrieving a return value from a DB2 stored procedure.
Method 1: Using OUT parameters
One way to retrieve a return value from a DB2 stored procedure is by using OUT parameters. These parameters are variables that are declared in the stored procedure and are used to return values back to the calling program.
Let's take a look at an example. Suppose we have a stored procedure called "get_employee_salary" that takes in an employee ID as a parameter and returns the employee's salary. We can define an OUT parameter called "salary" in the stored procedure and assign the employee's salary to it before the procedure ends.
CREATE PROCEDURE get_employee_salary (IN emp_id INT, OUT salary DECIMAL(10,2))
BEGIN
SELECT emp_salary INTO salary FROM employees WHERE emp_id = emp_id;
END
To call this stored procedure and retrieve the return value, we can use the following SQL statement:
CALL get_employee_salary(123, ?);
The question mark represents the OUT parameter, and the value of the employee's salary will be returned and stored in the variable.
Method 2: Using RETURN statement
Another way to retrieve a return value from a DB2 stored procedure is by using the RETURN statement. This statement allows us to return a value from the stored procedure to the calling program.
Let's modify our previous example to use the RETURN statement instead of OUT parameters.
CREATE PROCEDURE get_employee_salary (IN emp_id INT)
BEGIN
DECLARE salary DECIMAL(10,2);
SELECT emp_salary INTO salary FROM employees WHERE emp_id = emp_id;
RETURN salary;
END
To call this stored procedure and retrieve the return value, we can use the following SQL statement:
SELECT get_employee_salary(123) FROM SYSIBM.SYSDUMMY1;
The SELECT statement is used to call the stored procedure and retrieve the return value.
Method 3: Using a result set
We can also retrieve a return value from a DB2 stored procedure by using a result set. This method is useful when the stored procedure returns multiple values or a complex data structure.
Let's modify our previous example to return multiple values using a result set.
CREATE PROCEDURE get_employee_data (IN emp_id INT)
BEGIN
DECLARE c1 CURSOR WITH RETURN FOR
SELECT emp_name, emp_salary FROM employees WHERE emp_id = emp_id;
OPEN c1;
END
To call this stored procedure and retrieve the return values, we can use the following SQL statement:
CALL get_employee_data(123);
The result set will contain the employee's name and salary, which can be retrieved using a FETCH statement.
In conclusion, there are multiple ways to retrieve a return value from a DB2 stored procedure. Whether it is using OUT parameters, the RETURN statement, or a result set, it is important to understand the different methods and choose the one that best fits your needs. With these methods, you can easily retrieve data from your DB2 stored procedures and use it in your applications.
