Sure, I can definitely help you understand the RAISE_APPLICATION_ERROR procedure in Oracle SQL. It’s a built-in procedure in the DBMS_STANDARD package, used for displaying user-friendly error messages.
Oracle provides a mechanism for developers to display custom error messages to the users when a particular business rule or system requirement is not met. This procedure is known as RAISE_APPLICATION_ERROR.
RAISE_APPLICATION_ERROR is actually a procedure that’s part of the DBMS_STANDARD package. It allows developers to raise an exception and associate an error number and message to it. Its syntax is:
message VARCHAR2 [,
keep_error_stack BOOLEAN DEFAULT FALSE]);
The first argument (error_number) is the error number that can be between -20000 to -20999. The second argument is the message, which is a string used to display the error message. The third optional argument (keep_error_stack) is a Boolean argument that keeps track of the error stack or replaces it.
Let’s go through an example to understand it better.
The solution to the problem
Consider a bank where no customer is allowed to withdraw an amount more than 50000 at a time. We can raise an application error when the amount being withdrawn is more than 50000.
- The first step is to create a function that checks the withdrawal limit:
CREATE OR REPLACE FUNCTION check_withdrawl(p_withdrawl_amt IN NUMBER)
RETURN BOOLEAN AS
IF p_withdrawl_amt > 50000 THEN
RAISE_APPLICATION_ERROR(-20001,’You cannot withdraw more than 50000 at a time’);
- Next, call this function before the withdrawl action in the program, as follows:
l_result := check_withdrawl(60000);
WHEN OTHERS THEN
Working with Libraries and Understanding the DBMS_STANDARD Package
The DBMS_STANDARD package is a PL/SQL library that comes with Oracle Database. It contains many utility programs like subprograms, exceptions, and constants. One of them is the RAISE_APPLICATION_ERROR procedure, which we have used in our example.
Advanced Usage of RAISE_APPLICATION_ERROR
The RAISE_APPLICATION_ERROR procedure also allows you to keep the current error stack and add your message to it. This is useful when you want to know the whole execution path that led to the error. You can use the RAISE_APPLICATION_ERROR procedure in this advanced way by defining the third parameter as TRUE.
Remember, the main goal of this procedure is to provide a mechanism to communicate application-specific errors, which makes the code more reliable and easier for debugging and maintaining. By leveraging RAISE_APPLICATION_ERROR, Oracle SQL developers can improve the overall quality of their coding work.