Your range query lists five orders, then six on its rerun, because a new order arrived. Which anomaly is this?

• A phantom read
• A dirty read
• A deadlock

Your transaction reads 100, another commits 80, and your next read gets 80. Which anomaly is this?

• A dirty read
• A lost update
• A non-repeatable read

A dirty read sees data that was never committed.

Circle one:   True   False

Two transactions interleave to produce a phantom read. Which level would have prevented it?

• Read committed, which is enough for new rows
• Read uncommitted, the fastest choice
• Serializable, the level that forbids phantoms

Which level is the lowest one that forbids dirty reads?

• Read uncommitted
• Read committed
• Read approved

Which workload fits a weaker isolation level, and why?

• A rough analytics count, because a stale total harms nobody
• A bank balance, because money is simple
• A seat booking, because double booking is fine

Pat claims repeatable read also forbids phantoms, since both involve rereading. What is wrong?

• Nothing, the two anomalies are the same
• Repeatable read forbids dirty reads only
• Phantoms are new rows, not changed rows, and need serializable

A booking system runs at read committed and sometimes sells the last seat twice. Which level fixes it, and what does it forbid that the current one permits?

• Read uncommitted, which is faster and looser
• Serializable, which forbids the phantom that sneaks the second booking in
• No level can help, since seats are not rows