NEW and OLD record access in PostgreSQL - Cheat Sheet & Quick Revision

Recall & Review

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What does the NEW keyword represent in a PostgreSQL trigger?

NEW holds the new row data for INSERT or UPDATE operations inside a trigger function.

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What does the OLD keyword represent in a PostgreSQL trigger?

OLD holds the old row data for UPDATE or DELETE operations inside a trigger function.

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Can you use NEW in a DELETE trigger?

No. NEW is not available in DELETE triggers because no new row is created.

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In which trigger events is OLD available?

OLD is available in UPDATE and DELETE triggers because the old row exists before the change.

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How do you access the NEW record's column named price inside a trigger function?

Use NEW.price to get the value of the price column in the new row.

Which keyword gives you the old row data in a PostgreSQL trigger?

A NEW

B OLD

C CURRENT

D PREVIOUS

OLD holds the old row data before an update or delete.

In which trigger event can you use NEW?

A NONE

B DELETE

C TRUNCATE

D UPDATE

NEW is available in INSERT and UPDATE triggers, not DELETE.

What happens if you try to use NEW in a DELETE trigger?

A It causes an error

B It returns the deleted row

C It returns NULL

D It returns the new row

NEW is not defined in DELETE triggers and causes an error if accessed.

Which of these is true about OLD in triggers?

A Available in UPDATE and DELETE triggers

B Available in INSERT and UPDATE triggers

C Available only in INSERT triggers

D Never available

OLD is available in UPDATE and DELETE triggers.

How do you refer to the name column of the new row in a trigger?

A OLD.name

B CURRENT.name

C NEW.name

D ROW.name

NEW.name accesses the name column of the new row.

Explain the difference between NEW and OLD in PostgreSQL triggers.

Think about when rows are created, changed, or deleted.

Describe when you can access NEW and when you can access OLD in trigger functions.

Consider the lifecycle of a row during different operations.