第05章 排序与分页
创作日期:2021-11-20
1.排序数据
1.1 排序规则
1.2 单列排序
ASC (ascend):升序
SELECT first_name,salary FROM employees ORDER BY salary ASC;
(descend):降序
SELECT first_name,salary FROM employees ORDER BY salary DESC;
1.3 多列排序
二级排序
SELECT first_name,salary,department_id
FROM employees ORDER BY department_id ASC,salary ASC;
2.分页
2.1 背景
2.2 实现规则
SELECT employee_id,first_name,salary FROM employees LIMIT 0,10;
SELECT employee_id,first_name,salary FROM employees LIMIT 10,10;
2.3 扩展
SELECT TOP 5 name,hp_max FROM heros ORDER BY hp_max DESC
SELECT name,hp_max FROM heros ORDER BY hp_max DESC FETCH FIRST 5 ROWS ONLY
SELECT rownum,last_name,salary FROM employees WHERE rownum < 5 ORDER BY salary DESC
SELECT rownum,last_name,salary
FROM(
SELECT last_name,salary
FROM employees
ORDER BY salary DESC)
WHERE rownum < 10;
3.排序与分页练习
SELECT first_name,department_id,salary * 12 salary_year
FROM employees ORDER BY salary_year DESC,first_name ASC;
SELECT first_name,salary FROM employees
WHERE salary NOT BETWEEN 8000 AND 17000
ORDER BY salary DESC
LIMIT 20,20;
SELECT * FROM employees
WHERE email LIKE '%e%'
ORDER BY LENGTH(email) DESC,department_id ASC;
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