数据库的事物处理ISOLATION LEVEL

最新推荐文章于 2022-03-29 16:26:07 发布

转载最新推荐文章于 2022-03-29 16:26:07 发布 · 1.7k 阅读

文章标签：

#数据库 #database #types #sql

本文详细介绍了数据库事务的四种隔离级别：未提交读（Read uncommitted）、提交读（Read committed）、可重复读（Repeatableread）及串行化（Serializable）。分别阐述了每个级别如何处理脏读、不可重复读及幻读等问题。

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Serializable
Repeatable read
Read committed
Read uncommitted

Serializable
This level prohibits the following types of reads:
– Dirty reads: A transaction reads a database row containing uncommitted
changes from a second transaction.
– Nonrepeatable reads: One transaction reads a row, a second transaction
changes the same row, and the first transaction rereads the row and gets
a different value.
– Phantom reads: One transaction reads all rows that satisfy an SQL
WHERE condition, a second transaction inserts a row that also satisfies
the WHERE condition, and the first transaction applies the same WHERE
condition and gets the row inserted by the second transaction.

Repeatable read
This level prohibits dirty reads and nonrepeatable reads, but it allows
phantom reads.

Read committed
This level prohibits dirty reads, but allows nonrepeatable reads and phantom
reads.
Read uncommitted
This level allows dirty reads, nonrepeatable reads, and phantom reads.