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  3. Transactions and Error Handling in SQL Server

Exercise

Using the READ UNCOMMITTED isolation level

A new client visits your bank to open an account. You insert her data into your system, causing a script like this one to start running:

BEGIN TRAN

  INSERT INTO customers (first_name, last_name, email, phone)
  VALUES ('Ann', 'Ros', '[email protected]', '555555555')

  DECLARE @cust_id INT = scope_identity()

  INSERT INTO accounts (account_number, customer_id, current_balance)
  VALUES ('55555555555010121212', @cust_id, 150)

COMMIT TRAN

At that moment, your marketing colleague starts to send e-mails to every customer. There is going to be a raffle for a car! The script he executes gets every customer's data, including the last customer you inserted. This script starts running after the first insert occurs but before the COMMIT TRAN.

How can that be?

Instructions

100 XP
  • Set the READ UNCOMMITTED isolation level.
  • Select first_name, last_name, email and phone from customers table.