A nested transaction is a transaction that is started while in the middle of another transaction. In this relationship, the transaction that is started first is the parent and the transaction that is started in the middle of the parent transaction is the child transaction.
To start a nested transaction, simply call another START TRANSACTION before the current transaction is validated or cancelled.
Cancelling the parent transaction cancels all child transactions, but cancelling a child transaction does not affect the parent transaction.
It is possible to nest up to 32,767 levels of transactions.