Achieve Consistent Data with REPEATABLE READ

Set Transaction Isolation Level to REPEATABLE READ

Write a PostgreSQL query to set the transaction isolation level to REPEATABLE READ for a transaction.

Solution:

-- Begin the transaction and set isolation level to REPEATABLE READ.
BEGIN;
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
-- (Perform transactional operations here)
COMMIT;

Explanation:

• Purpose of the Query:
• The goal is to ensure that all reads within the transaction see a consistent snapshot of the data.
• This demonstrates how to use REPEATABLE READ to avoid non-repeatable reads.
• Key Components:
• SET TRANSACTION ISOLATION LEVEL REPEATABLE READ; : Sets the desired isolation level for consistency.
• Real-World Application:
• Ideal for financial applications or reporting systems where a consistent view of data is critical.

Notes:

• REPEATABLE READ prevents non-repeatable reads but may still allow phantom reads.
• It guarantees that repeated queries within the same transaction return the same result set.

For more Practice: Solve these Related Problems:

• Write a PostgreSQL query to update an employee’s salary in the Employees table within a REPEATABLE READ transaction and verify that repeated SELECTs return the same result.
• Write a PostgreSQL query to insert a new record into the Products table using REPEATABLE READ isolation and then perform a subsequent SELECT to confirm a consistent snapshot.
• Write a PostgreSQL query to update a student's grade in the Students table within a transaction set to REPEATABLE READ isolation.
• Write a PostgreSQL query to delete an outdated order from the Orders table within a transaction using REPEATABLE READ isolation.

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Previous PostgreSQL Exercise: Using Isolation Level to Prevent Dirty Reads.
Next PostgreSQL Exercise: Set Transaction Isolation Level to SERIALIZABLE.