1. Outside a transaction, run SHOW transaction_isolation;. What is the default level?
2. Start a transaction at REPEATABLE READ. Then show its level.
3. End that transaction. Start a new one, run SELECT * FROM accounts;, then try to set the level to SERIALIZABLE. What must SET TRANSACTION come before? End the aborted transaction.
4. Start a transaction at SERIALIZABLE the right way and show its level.
5. A MySQL server runs with the default settings. Which isolation level does a new transaction get?