Repeatable Reads (REPEATABLE-READS)
- Consistent reads within same transaction
- Even if the other transaction has commited the changes, the changes wouldn’t occur in the current transaction (Unless the current transaction is commited)
Read Commited (READ-COMMITED)
- Reads within the same transaction always reads the fresh/latest values
- The only con being, multiple reads within the same transaction is not consistent
- If the other transaction has commited the changes, the changes will occur in the current transaction (Only if the other transaction is commited)
Read Uncommited (READ-UNCOMMITED)
- Reads the uncommited values in the other transaction (Which is not the case with other Isolation Levels)
- This is called as a “Dirty Read“ Problem
- Gives you slightly higher throughput
Serializable (SERIALIZABLE)
- Every read is a locking read (Depends on engine though)
- While one transaction reads, others will have to wait
- So basically, every read that you do is locking read