NOLOCK equivalent in MySQL

Mohsin's DBA Blog

SQL Server WITH (NOLOCK) looks like this:

SELECT * FROM TABLE WITH (nolock)

To achieve the same with MySQL, we change the session isolation mode using the SET SESSION command.

SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED ;
SELECT * FROM TABLE_NAME ;
SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ ;

This statement will work similar to WITH (NOLOCK) i.e READ UNCOMMITTED data. We can also set the isolation level for all connections globally:

SET GLOBAL TRANSACTION ISOLATION LEVEL READ UNCOMMITTED ;

In addition, two system variables related to isolation also level exist in MySQL:

--global isolation level
SELECT @@global.tx_isolation; 
--session isolation level
SELECT @@tx_isolation; 

Or set the isolation level inside a transaction:

SET TRANSACTION ISOLATION LEVEL REPEATABLE READ

MySQL Isolation levels documentation is here

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