数据库事务 --- Database Transaction

• 什么是事务(transaction)
• ACID性质
• • 原子性(Atomicity)
  • 一致性(Consistency)
  • 隔离性(Isolation)
  • 持久性(Durability)
• 数据库冲突 -- Conflicts
• • serial execution
  • Read-Write (RW) ---- "unrepeatable reads"
  • Write-Read (WR) --- "dirty reads"
  • Write-Write (WW) --- "lost updates"
  • 幻读 --- Phantom Problem
  • Different Transaction Type
• 数据库隔离-- Isolation
• • SQL Isolation Level
  • 如何实现Isolation
• 数据库恢复 -- Recovery

什么是事务(transaction)

ACID性质

原子性(Atomicity)

一致性(Consistency)

隔离性(Isolation)

持久性(Durability)

数据库冲突 – Conflicts

serial execution

Read-Write (RW) ---- “unrepeatable reads”

Write-Read (WR) — “dirty reads”

Write-Write (WW) — “lost updates”

幻读 — Phantom Problem

Different Transaction Type

Read-Only Transaction

SET TRANSACTION READ ONLY; 
SELECT * FROM Accounts 
WHERE account#=‘1234’;

Read-Write Transaction

SET TRANSACTION READ WRITE; 
update Accounts
set balance = balance - $100
where account#= ‘1234’; .

数据库隔离-- Isolation

SQL Isolation Level

READ UNCOMMITTED

READ COMMITTED

REPEATABLE READ

SERIALIZABLE

如何实现Isolation

READ UNCOMMITTED

READ COMMITTED

REPEATABLE READ

SERIALIZABLE

数据库恢复 – Recovery

Mirroring

Backup

System Logging