可序列化和可重复读取隔离级别有什么区别？

Question

What is the difference between serializable and repeatable read isolation level? Can anyone please give a simple example.

Answer 1

Summary:

In a Repeatable Read isolation level, new rows can be inserted into the dataset.

In a Serializable isolation level all the rows are locked for the duration of the transaction, no insert,update or delete is allowed.

Please refer this for examples and explanation

Isolation Level - serializable

http://beyondrelational.com/modules/2/blogs/28/posts/10467/sql-server-transaction-isolation-level-serializable.aspx

Isolation Level - repeatable-read

http://beyondrelational.com/modules/2/blogs/28/posts/10466/sql-server-transaction-isolation-level-repeatable-read.aspx

Answer 2

Repeatable read prevents only non-repeatable read (so you can read the same data in the same transaction without fear of someone changing it - even though it's a rare need for doing it).

Serializable prevents both non-repeatable read and phantom rows (so you can't even INSERT data). That means you can READ and WRITE (SELECT, UPDATE) rows that are not included with serializable transaction, but you can't DELETE OR INSERT rows on TABLE level.

Both repeatable read and serializable are very strict and there is not always need for them!

Answer 3

besides above, different implement is differed.

such as mysql, the repeatable read will not cause phantom problem. as document

SERIALIZABLE enforces even stricter rules than REPEATABLE READ, and is used mainly in specialized situations, such as with XA transactions and for troubleshooting issues with concurrency and deadlocks.