Oracle :
- default : READ COMMITED ( 오라클은 READ COMMITED와 SERIALIZABLE READ 만 지원)
Default Isolation Oracle uses is Read Committed. You may think that means Oracle allows Non-repeatable Read. But this doesn’t tell us whole story. Oracle doesn’t follow SQL Standard exactly, as per SQL standard Repeatable Read is the isolation level which guarantees a read-consistent result from a query. As per SQL standard definition Read committed doesn’t give us consistent results and Read uncommitted is the level to get non-blocking reads.
However the way oracle implemented Read Committed transaction, it has all attributes to get you read consistent data. This is not true for other databases, Read Committed can return answers which never existed. Oracle also supports idea of Read Uncommitted as it never blocks read.
Mysql(InnoDB) :
- default : REPEATABLE READ
