大家帮我看看这道题应该选哪一个？

chenfeng

Which statement about executing a Data Manipulation Language(DML)
SQL statement is true?
A.The data block is updated to record the new values of the data.
B.The Oracle server places shared locks on the rows that are to be modified.
C.The rollback segment records the after-image of the changes to the data block.
D.If the data and rollback blocks are not already in the buffer cache,Oracle will terminate the SQL statement.

我觉得这道题的答案应该选B，而TK的答案是选A，我不明白为什么？请大家帮我解释一下！

kingbird

A是正确的

当修改数据时，oracle给该行加排它锁，而不是共享锁

当做查询时加共享锁