题目描述
存在如下的视图:
create view emp_v as select * from employees where emp_no >10005;
如何获取emp_v和employees有相同的数据?
CREATE TABLE `employees` (
`emp_no` int(11) NOT NULL,
`birth_date` date NOT NULL,
`first_name` varchar(14) NOT NULL,
`last_name` varchar(16) NOT NULL,
`gender` char(1) NOT NULL,
`hire_date` date NOT NULL,
PRIMARY KEY (`emp_no`));
输出格式:
emp_no birth_date first_name last_name gender hire_date
10006 1953-04-20 Anneke Preusig F 1989-06-02
10007 1957-05-23 Tzvetan Zielinski F 1989-02-10
10008 1958-02-19 Saniya Kalloufi M 1994-09-15
10009 1952-04-19 Sumant Peac F 1985-02-18
10010 1963-06-01 Duangkaew Piveteau F 1989-08-24
10011 1953-11-07 Mary Sluis F 1990-01-22
解决思路
视图 emp_v 是从 employees 中导出的,所以要判断两者中相等的数据,只需要判断emp_no相等即可
- 方法一:用 WHERE 选取二者 emp_no 相等的记录
SELECT em.* FROM employees AS em, emp_v AS ev WHERE em.emp_no = ev.emp_no
- 方法二:用 INTERSECT 关键字求 employees 和 emp_v 的交集
SELECT * FROM employees INTERSECT SELECT * FROM emp_v