Incorrect concurrency can lead to problems such as dirty reads , phantom reads , and non - repeatable reads 不正确的并发可能导致脏读、幻读和不可重复读等问题。
For the four levels of isolation supported , table 6 shows whether phantom , dirty , or non - repeatable read is possible from strongest to weakest 针对受支持的四种隔离级别,表6列出了出现幻像读、脏读或不可重复读的可能性(从高到低) 。
Data can be changed by other transactions between individual statements within the current transaction , resulting in nonrepeatable reads or phantom data 其他事务可以在当前事务的各个语句之间更改数据,从而产生不可重复读取和幻像数据。
Unrepeatable read ? a transaction reads a row twice and reads different state each time . for example , another transaction may have written to the row , and committed , between the two reads 不可重复读一个事务对同一行数据重复读取两次,但是却得到了不同的结果。例如,在两次读取的中途,有另外一个事务对该行数据进行了修改,并提交。