This document provides examples of validation trigger code that can be integrated into existing code. The examples check for 1) empty textboxes, 2) duplicate IDs, 3) textbox length, 4) value ranges for numbers, and 5) dates being before the current date. The code uses IF/THEN statements to check conditions and raise errors or continue processing based on the validation checks.

1. Extracts of validation trigger examples
You can integrate the following codes in existing code for different validation triggers:
1. Check if a textbox is filled
IF :STUDENT_INSERT.STUDENT_ID IS NULL THEN
MESSAGE('You have not inserted a student ID yet');
RAISE FORM_TRIGGER_FAILURE;
ELSE NULL;
END IF;
2. Check ID/candidate key duplication
DECLARE
ID_COUNT Number(3);
BEGIN
‐‐Count the number of student record in the database, given the ID insered by the user, put into
ID_COUNT variable
SELECT COUNT(*) INTO ID_COUNT FROM STUDENT WHERE
LOWER(STUDENT_ID)=LOWER(:STUDENT_INSERT.STUDENT_ID);
‐‐If there more more than 1 record with this ID, show error
IF ID_COUNT>0 THEN
MESSAGE('This ID has been used, please use the other one.');
RAISE FORM_TRIGGER_FAILURE;
ELSE
MESSAGE('You can use this ID');
END IF;

2. 3. Check length of a textbox
‐‐Check the length of the textbox user typed, prompt error when the size less than 8
IF LENGTH(:student_insert.student_id) != 8
THEN message('Student ID should be in 8‐character, please re‐try.');
RAISE FORM_TRIGGER_FAILURE;
ELSE NULL;
END IF;
4. Range check (for numbers)
‐‐Check the range, prompt error if user types less than 0 or more than 5
IF:STUDENT_INSERT.YEAR<0
THEN MESSAGE('The Year of Study should be a positive number.');
RAISE FORM_TRIGGER_FAILURE;
ELSIF :STUDENT_INSERT.YEAR>5
THEN MESSAGE('The Year of Study should be less than 5.');
RAISE FORM_TRIGGER_FAILURE;
ELSE NULL;
END IF;
5. Check date inserted must be before the current date
IF :STUDENT_INSERT.DOB>SYSDATE
THEN MESSAGE('The date of birth cannot be a future date');
RAISE FORM_TRIGGER_FAILURE;
ELSE NULL;
END IF;