As the Accountant, execute the following statements to enable snapshot isolation for the database and to specify the snapshot isolation level that is used:

SET OPTION PUBLIC.allow_snapshot_isolation = 'On';
SET TEMPORARY OPTION isolation_level = 'snapshot';

As the Accountant, execute the following statement to list the prices of the visors:

SELECT ID, Name, UnitPrice
FROM GROUPO.Products
ORDER BY ID;

As the Sales Manager, execute the following statements to introduce a new sale price for the plastic visor:

UPDATE GROUPO.Products
SET UnitPrice = 5.95 WHERE ID = 501;
COMMIT;
SELECT ID, Name, UnitPrice FROM GROUPO.Products
WHERE Name = 'Visor';

The Accountant executes his query again and does not see the change in price because the data that was committed at the time of the first read is used for the transaction.

SELECT ID, Name, UnitPrice
FROM GROUPO.Products;

As the Sales Manager, change the plastic visor back to its original price:

UPDATE GROUPO.Products
SET UnitPrice = 7.00
WHERE ID = 501;
COMMIT;

The database server does not place a read lock on the rows in the Products table that the Accountant is reading because the Accountant is viewing a snapshot of committed data that was taken before the Sales Manager made any changes to the Products table.

The Accountant is finished looking at the prices. He doesn't want to risk accidentally changing the database, so he completes his transaction with a ROLLBACK statement.

ROLLBACK;