This SNOW-CAD practice question tests your understanding of automating application logic with business rules and scripts. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A developer writes a Business Rule to calculate a total on an Aggregate field. The rule runs on 'insert' and 'update' on the parent table. However, the total is not updating correctly when child records are deleted. Why?
The Business Rule should use 'current' and 'previous' to detect deletion.
Why wrong: Previous is not available in delete context.
The Business Rule should be on the child table's delete event.
Child delete triggers need separate rule on child table.
The Business Rule should also run on 'delete'.
Why wrong: Delete of parent not relevant.
The Business Rule should be a Global Business Rule.
Why wrong: Global rule does not solve trigger issue.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The Business Rule should be on the child table's delete event.
A Business Rule that runs on 'insert' and 'update' on the parent table will not fire when a child record is deleted, because the delete event occurs on the child table, not the parent. To correctly update an aggregate field on the parent when child records are deleted, the Business Rule must be defined on the child table's 'delete' event. This ensures the rule executes when the child record is removed, allowing the aggregate to be recalculated.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The Business Rule should use 'current' and 'previous' to detect deletion.
Why it's wrong here
Previous is not available in delete context.
The Business Rule should be on the child table's delete event.
Why this is correct
Child delete triggers need separate rule on child table.
Related concept
Read the scenario before looking for a memorised answer.
The Business Rule should also run on 'delete'.
Why it's wrong here
Delete of parent not relevant.
The Business Rule should be a Global Business Rule.
Why it's wrong here
Global rule does not solve trigger issue.
Common exam traps
The trap here is that candidates assume a Business Rule on the parent table with a 'delete' event will catch child deletions, but in ServiceNow, the delete event only fires on the table where the record is actually deleted, not on related parent records.
Detailed technical explanation
In ServiceNow, Business Rules are table-specific and event-driven; they only execute when the specified event (insert, update, delete, or query) occurs on the table they are defined on. When a child record is deleted, the parent table does not experience a delete event—only the child table does. Therefore, to update a parent aggregate field, the rule must be placed on the child table with the 'delete' event, and within the script, use 'current.parent' to reference and update the parent record.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the SNOW-CAD exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Automating application logic with business rules and scripts — This question tests Automating application logic with business rules and scripts — Read the scenario before looking for a memorised answer..
The correct answer is: The Business Rule should be on the child table's delete event. — A Business Rule that runs on 'insert' and 'update' on the parent table will not fire when a child record is deleted, because the delete event occurs on the child table, not the parent. To correctly update an aggregate field on the parent when child records are deleted, the Business Rule must be defined on the child table's 'delete' event. This ensures the rule executes when the child record is removed, allowing the aggregate to be recalculated.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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