2020 主流關聯式資料庫的預設交易隔離層級 relational database default transaction isolation levels

2020 主流關聯式資料庫的預設交易隔離層級(SQL-transaction isolation level)如下。

• Oracle 18c:READ COMMITED
• MySQL 8.0 (InnoDB):REPEATABLE READ
• SQL Server 2019:READ COMMITTED (READ_COMMITTED_SNAPSHOT OFF)
• PostgreSQL 13:READ COMMITTED
• MariaDB 10.5(InnoDB):REPEATABLE READ
• AWS Aurora MySQL:REPEATABLE READ
• GCP Cloud SQL MySQL instances:REPEATABLE READ
• GCP Cloud SQL PostgreSQL instances:READ COMMITTED
• Azure SQL Database:READ COMMITTED (READ_COMMITTED_SNAPSHOT ON)
• H2:READ COMMITTED

各資料庫隔離層級基本上都在READ COMMITTED層級以上，也就是不會有髒讀(dirty read)的現象。

• DB-Engines Ranking
• ANSI SQL-92 SQL-transaction isolation level