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  3. Transactions and Error Handling in PostgreSQL

Exercise

Using an isolation level

As seen in the video, sometimes it's important to be able to select an isolation level for an individual transaction. It's best to use START TRANSACTION to do this which is an alias of BEGIN TRANSACTION to make it clear something is different. You can specify an ISOLATION LEVEL when starting the transaction.

Here we are going to use REPEATABLE READ which protects us from dirty reads, nonrepeatable reads, and phantom reads. In the FFEIC data, RCON2210 is the demand deposits field, and tracks all outstanding checking accounts, bank-issued checks and unposted credits. They can be a liability to a bank if there was a funds rush for any reason. Let's find all those banks with over $100,000,000 in demand deposits.

Instructions

100 XP
  • Start a transaction with repeatable read.
  • Select all the records with RCON2210 over $100,000,000 in demands deposits.
  • Select all the records with RCON2210 still over $100,000,000 in demands deposits.
  • Commit the transaction.