提交读 READ COMMITTED ; READ COMMITED ; commited read ; C
读未提交 READ UNCOMMITTED
读已提交 Read committed
已提交读 Read Committed
设置读提交级别 set transaction isolation level read committed
读取未提交 Read Uncommitted
读取已提交 Read Committed
未提交的读 Uncommitted Read ; No Yes Yes Yes ; READ UNCOMMITTED
读取未提交内容 READ UNCOMMITTED
在读事务中，没有变更需要提交，但是事务会防止对正在被读取的数据的修改，直到所有的读操作全部结束。
In a read transaction, there are no changes to commit, but the transaction prevents the data being read from changing until all of the reads are complete.
将分割镜像初始化为快照时，将执行崩溃恢复，回滚所有未提交的事务，并使数据库可以被所有读或写操作访问。
The initialization of the split mirror as snapshot performs a crash recovery, rolls back all uncommitted transactions, and makes the database available for any read or write operation.
读事务需要数据的一致视图 —— 即当同时提交两个读事务时，如果它们选择相同的数据范围，那么应该产生一致的结果集。
Read transactions require a consistent view of the data -- meaning if two read transactions are submitted at the same time, they should produce uniform result sets if they select the same data ranges.
应用推荐