158. Which statements are true regarding the FOR UPDATE clause in a SELECT statement? (Choose all
that apply.)
A. It locks only the columns specified in the SELECT list.
B. It locks the rows that satisfy the condition in the SELECT statement.
C. It can be used only in SELECT statements that are based on a single table.
D. It can be used in SELECT statements that are based on a single or multiple tables.
E. After it is enforced by a SELECT statement, no other query can access the same rows until a
COMMIT or ROLLBACK is issued.
Answer: BD
答案解析：
参考：http://blog.csdn.net/rlhua/article/details/12885143
A，只锁定SELECT列表中指定的列，错误，是指定的行。
B，锁定SELECT语句中满足条件的行，正确。
C，只能用于基于单个表的SELECT语句中，错误。可以针对多个表在SELECT语句中使用FOR UPDATE子句。
D，可以用于基于单个表或多个表的SELECT语句中，正确。
E，用SELECT语句执行之后，其它查询直到执行COMMIT或ROLLBACK后才能访问相同的行，错误，即使被锁定，也是可以查询的。