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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