oracle select case语句

Oracle数据库中的SELECT CASE语句是一种条件选择语句，根据一定的条件执行不同的操作。以下是十个使用Oracle SELECT CASE语句的示例：

1. 根据员工的工资等级查询员工姓名： ```sql

SELECT employee_name, CASE

WHEN salary > 5000 THEN '高级员工' WHEN salary > 3000 THEN '中级员工' ELSE '初级员工' END AS salary_level FROM employees; ```

2. 根据学生成绩判断学生的等级： ```sql

SELECT student_name, CASE

WHEN score >= 90 THEN '优秀' WHEN score >= 80 THEN '良好' WHEN score >= 70 THEN '中等'

ELSE '不及格' END AS grade FROM students; ```

3. 根据订单状态查询订单的描述信息： ```sql

SELECT order_id, CASE

WHEN status = 'NEW' THEN '新订单'

WHEN status = 'PROCESSING' THEN '处理中' WHEN status = 'COMPLETED' THEN '已完成' ELSE '未知状态'

END AS status_description FROM orders; ```

4. 根据产品类型查询产品的价格范围： ```sql

SELECT product_name, CASE

WHEN product_type = 'Electronics' THEN '1000-5000元'

WHEN product_type = 'Clothing' THEN '200-1000元' WHEN product_type = 'Books' THEN '10-200元' ELSE '未知价格范围' END AS price_range FROM products; ```

5. 根据用户的年龄段查询用户的性别： ```sql

SELECT user_name, CASE

WHEN age BETWEEN 18 AND 25 THEN '男' WHEN age BETWEEN 26 AND 35 THEN '女' ELSE '未知' END AS gender FROM users; ```

6. 根据学生的出勤情况判断是否获得奖学金： ```sql

SELECT student_name, CASE

WHEN attendance >= 90 AND grade >= 80 THEN '获

得奖学金'

ELSE '未获得奖学金' END AS scholarship FROM students; ```

7. 根据员工的工作年限查询员工的职称： ```sql

SELECT employee_name, CASE

WHEN years_of_service >= 10 THEN '高级工程师' WHEN years_of_service >= 5 THEN '中级工程师' ELSE '初级工程师' END AS job_title FROM employees; ```

8. 根据学生成绩判断学生的学习状态： ```sql

SELECT student_name, CASE

WHEN score >= 90 THEN '优秀' WHEN score >= 80 THEN '良好'

WHEN score >= 60 THEN '及格' ELSE '不及格' END AS study_status FROM students; ```

9. 根据产品的库存量查询产品的供应状态： ```sql

SELECT product_name, CASE

WHEN stock > 0 THEN '有货' ELSE '缺货'

END AS supply_status FROM products; ```

10. 根据用户的会员等级查询用户的折扣率： ```sql

SELECT user_name, CASE

WHEN membership_level = 'Gold' THEN '8折' WHEN membership_level = 'Silver' THEN '9折' WHEN membership_level = 'Bronze' THEN '95折'

ELSE '无折扣'

END AS discount_rate FROM users; ```

以上是十个使用Oracle SELECT CASE语句的示例，通过SELECT CASE语句可以根据不同的条件进行灵活的数据查询和操作，使查询结果更具有可读性和可理解性。