html网站-关于发展历程的案例-CFANZ编程社区

1.自定义排序（ORDER BY FIELD）

CREATE TABLE movies (  
  id INT PRIMARY KEY AUTO_INCREMENT,  
  movie_name VARCHAR(255),  
  actors VARCHAR(255),  
  price DECIMAL(10, 2) DEFAULT 50,  
  release_date DATE  
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

INSERT INTO movies (movie_name, actors, price, release_date) VALUES
('咱们结婚吧', '靳东', 43.2, '2013-04-12'),
('四大名捕', '刘亦菲', 62.5, '2013-12-21'),
('猎场', '靳东', 68.5, '2017-11-03'),
('芳华', '范冰冰', 55.0, '2017-09-15'),
('功夫瑜伽', '成龙', 91.8, '2017-01-28'),
('惊天解密', '靳东', 96.9, '2019-08-13'),
('铜雀台', null, 65, '2025-12-16'),
('天下无贼', '刘亦菲', 44.9, '2004-12-16'),
('建国大业', '范冰冰', 70.5, '2009-09-21'),
('赛尔号4：疯狂机器城', '范冰冰', 58.9, '2021-07-30'),
('花木兰', '刘亦菲', 89.0, '2020-09-11'),
('警察故事', '成龙', 68.0, '1985-12-14'),
('神话', '成龙', 86.5, '2005-12-22');

select * from movies order by movie_name asc;

select * from movies ORDER BY FIELD(movie_name,'神话','猎场','芳华','花木兰',
'铜雀台','警察故事','天下无贼','四大名捕','惊天解密','建国大业',
'功夫瑜伽','咱们结婚吧','赛尔号4：疯狂机器城');

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2.空值NULL排序（ORDER BY IF(ISNULL）)

select * from movies ORDER BY actors, price desc;

select * from movies ORDER BY if(ISNULL(actors),0,1), actors, price;

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3.CASE表达式（CASE···WHEN）

CREATE TABLE student (
  student_id varchar(10) NOT NULL COMMENT '学号',
  sname varchar(20) DEFAULT NULL COMMENT '姓名',
  sex char(2) DEFAULT NULL COMMENT '性别',
  age int(11) DEFAULT NULL COMMENT '年龄',
  score float DEFAULT NULL COMMENT '成绩',
  PRIMARY KEY (student_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='学生表';

INSERT INTO student (student_id, sname, sex, age , score)
VALUES ('001', '张三', '男', 20,  95),
       ('002', '李四', '女', 22,  88),
       ('003', '王五', '男', 21,  90),
       ('004', '赵六', '女', 20,  74),
       ('005', '陈七', '女', 19,  92),
       ('006', '杨八', '男', 23,  78),
       ('007', '周九', '女', 20,  55),
       ('008', '吴十', '男', 22,  91),
       ('009', '刘一', '女', 21,  87),
       ('010', '孙二', '男', 19,  60);

select *,case when score > 90 then '优秀'
			when score > 80 then '良好'
			when score > 60 then '一般'
			else '较差' end level
from student;

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4.分组连接函数（GROUP_CONCAT）

select actors,
GROUP_CONCAT(movie_name),
GROUP_CONCAT(price) from movies GROUP BY actors;

select actors,
GROUP_CONCAT(movie_name order by price desc SEPARATOR '_'),
GROUP_CONCAT(price order by price desc SEPARATOR '_') 
from movies GROUP BY actors;

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5.分组统计数据后再进行统计汇总（with rollup）

SELECT actors, SUM(price) FROM movies GROUP BY actors;

SELECT actors, SUM(price) FROM movies GROUP BY actors WITH ROLLUP;

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6.子查询提取（with as）

with m1 as (select * from movies where price > 50),
 m2 as (select * from movies where price >= 65)
select * from m1 where m1.id not in (select m2.id from m2) and m1.actors = '刘亦菲';

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7.优雅处理数据插入、更新时主键、唯一键重复

select * from movies where id >= 13;

INSERT INTO movies (id, movie_name, actors, price, release_date) VALUES
(13, '神话', '成龙', 100, '2005-12-22');

INSERT IGNORE INTO movies (id, movie_name, actors, price, release_date) VALUES
(13, '神话', '成龙', 100, '2005-12-22');

INSERT IGNORE INTO movies (id, movie_name, actors, price, release_date) VALUES
(14, '神话2', '成龙', 114, '2005-12-22');

REPLACE INTO movies (id, movie_name, actors, price, release_date) VALUES
(14, '神话2', '成龙', 100, '2005-12-22');

REPLACE INTO movies (id, movie_name, actors, price, release_date) VALUES
(15, '神话3', '成龙', 115, '2005-12-22');

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INSERT INTO movies (id, movie_name, actors, price, release_date) VALUES
(15, '神话3', '成龙', 115, '2005-12-22') on duplicate key update price = price + 10;

INSERT INTO movies (id, movie_name, actors, price, release_date) VALUES
(16, '神话4', '成龙', 75, '2005-12-22') on duplicate key update price = price + 10;

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