Quiz: Read Committed

Grab a pen and notepad, and jot down your answers as you go, then check your answers at the key at the bottom of the page.

Questions

Q1. For a SELECT query running under read committed, locks are held….

1.  For the duration of the statement
2.  For the duration of the transaction
3.  For a very short time
4.  Until the Deadlock Monitor wakes up

Q2. SELECT queries running under read committed like to use….

1.  Exclusive locks
2.  Key range locks
3.  Shared locks
4.  Schema modification locks

Q3. Queries running under read committed may read the same row multiple times.

1.  True
2.  False

Q4. Queries running under read committed may miss some rows and not read them at all.

1.  True
2.  False

Q5. Queries running under read committed always use row level locks.

1.  True
2.  False

Q6. Fill in the blank: Read committed is a transaction ______ level in SQL Server.

Q7. Read committed is the default isolation level in SQL Server, EXCEPT in…

1.  Azure SQL Database
2.  SQL Server Failover Cluster Instances
3.  SQL Server RDS (Amazon)
4.  On-premises SQL Server installations

Scroll down for the answer key :point_down:

Answer Key

• A1. 3. For a very short time
• A2. 3. Shared locks
• A3. 1. True
• A4. 1. True
• A5. 2. False. The engine may decide to start with a page level lock, and lock escalation is possible as well.
• A6. isolation
• A7. 1. Azure SQL Database. Note: there’s an additional correct answer not in this list, which is readable secondaries in Availability Groups! Check out the course on Snapshot Isolation Against Readable Secondaries for more information on that.