SQL Update/Delete Constraints | Dataford Interview Questions

Explain how you would delete or update rows in Salesforce using only SELECT and INSERT operations.

Provide a PostgreSQL statement that reads the Salesforce contact snapshot and inserts a change plan representing required updates or deletions. Do not directly modify the snapshot table.

Output

One row per eligible contact, with plan_id, contact_id, operation, replacement_status, and replacement_phone.
Include inactive contacts, contacts with missing phone numbers, and deleted contacts. Sort by contact_id ascending.

Schema

salesforce_contact_snapshot

Column	Type	Description
contact_idPK	INT	Salesforce Contact identifier
status	VARCHAR(20)	Current Contact status
phone	VARCHAR(20)	Current phone number
is_deleted	BOOLEAN	Whether Salesforce marked the Contact as deleted

salesforce_contact_change_plan

Column	Type	Description
plan_idPK	INT	Change plan identifier
contact_id	INT	Referenced Salesforce Contact identifier
operation	VARCHAR(10)	Planned operation, UPDATE or DELETE
replacement_status	VARCHAR(20)	Status to apply for an update
replacement_phone	VARCHAR(20)	Phone number to apply for an update

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Problem