Return a book

Let's say the borrowing record with ID 1 has been returned. We can update it with:

code sql

UPDATE borrow
SET borrow_return_date = CURRENT_TIMESTAMP
WHERE borrow_id = 1
  AND borrow_return_date IS NULL;

Then check the record:

code sql

SELECT * FROM borrow;

Record 1 should now contain a value in:

code text

borrow_return_date

The record is no longer considered an active borrowing transaction.

Why check borrow_return_date IS NULL in the UPDATE?

It prevents the same borrowing record from being "returned" again after it has already been returned.

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