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047-108

原创 Linux操作系统 作者:jbymy2000 时间:2012-03-19 09:09:37 0 删除 编辑
108. View the Exhibit and examine the details for the CATEGORIES_TAB table.
Evaluate the following incomplete SQL statement:
SELECT category_name,category_description
FROM categories_tab
You want to display only the rows that have 'harddisks' as part of the string
in the CATEGORY_DESCRIPTION column.
Which two WHERE clause options can give you the desired result? (Choose two.)
A. WHERE REGEXP_LIKE (category_description, 'hard+.s');
B. WHERE REGEXP_LIKE (category_description, '^H|hard+.s');
C. WHERE REGEXP_LIKE (category_description, '^H|hard+.s$');
D. WHERE REGEXP_LIKE (category_description, '[^H|hard+.s]');
Answer: AB
正则表达式规则: [^. . .] --- A “not equals” bracket expression
| --- Logical OR.
. --- Match any character in the database character set.
$ --- End of line anchor
^ --- Beginning of line anchor.
+ ----Match one or more occurrences of the preceding subexpression.
Occurrences:正在发生的 expression:表达式
Eg:
update emp set ename='harddisks' where emp_no=5;
select * from emp where REGEXP_LIKE (ename, '^H|hard+.s');
select * from emp where REGEXP_LIKE (ename, 'H|hard+.s');
select * from emp where REGEXP_LIKE (ename, 'hard+.s');
可以查出数据
select * from emp where REGEXP_LIKE (ename, 'H|hard+.s$');
无任何数据

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