Isolation Levels

MySQL InnoDB supports four isolation levels controlling the visibility of uncommitted changes from other transactions.

Example

-- Set isolation level (session)
SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;
-- Levels (weakest → strongest):
-- READ UNCOMMITTED: sees dirty reads (uncommitted data)
-- READ COMMITTED:   no dirty reads; non-repeatable reads possible
-- REPEATABLE READ:  default; consistent snapshot within transaction
-- SERIALIZABLE:     locks all reads; slowest, safest
SET GLOBAL TRANSACTION ISOLATION LEVEL REPEATABLE READ;

SQL

Full Editor

Pro Tip

REPEATABLE READ is MySQL's default and prevents most anomalies without full SERIALIZABLE locking.

Related Resources

MySQL Reference

Complete tag & property list

MySQL How-To Guides

Step-by-step practical guides

MySQL Exercises

Practice what you've learned