OCP-1Z0-051 第170题 DELETE的注意事项
一、原题Which two statements are true regarding the DELETE and TRUNCATE commands? (Choose two.)
A. DELETE can be used to remove only rows from only one table at a time.
B. DELETE can be used to remove only rows from multiple tables at a time.
C. DELETE can be used only on a table that is a parent of a referential integrity constraint.
D. DELETE can be used to remove data from specific columns as well as complete rows.
E. DELETE and TRUNCATE can be used on a table that is a parent of a referential integrity constraint having ON DELETE rule.
答案：AE
二、题目翻译
关于DELETE和TRUNCATE命令哪两个句子是正确的？(选择两个)
A.DELETE一次只能用于移除一个表的行。
B.DELETE一次只能用于移除多个表的行。
C.DELETE只能用于删除有引用完整性约束的父表。
D.DELETE可以用于删除指定列的数据以及完整的行。
E.DELETE和TRUNCATE可以用于有引用完整性约束ON DELETE规则的父表。
三、题目解析
表可以使用ON DELETE CASCADE选项（当删除父表数据时，子表数据也一起删除）或ON DELETE CASCAD SET NULL选项（当删除父表数据时，子表相关的列设置为NULL）,
有这些选项，就可以在父表中直接删除相关的行，而不会报外键约束错误。
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