Java mysql特殊形式的查询语句详解

-- 创建学员表
CREATE TABLE IF NOT EXISTS stu(
id TINYINT UNSIGNED AUTO_INCREMENT KEY COMMENT '编号',
username VARCHAR(20) NOT NULL UNIQUE COMMENT '学员名称',
score TINYINT UNSIGNED NOT NULL COMMENT '学员考试分数'
)ENGINE=INNODB;

INSERT stu(username, score) VALUES('king', 95),
('queen', 75),
('zhangsan', 69),
('lisi', 78),
('wangwu', 87),
('zhaoliu', 88),
('tianqi', 98),
('ceshi', 99),
('tiancai', 50);

-- 创建分数级别表
CREATE TABLE IF NOT EXISTS `level`(
id TINYINT UNSIGNED AUTO_INCREMENT KEY COMMENT '编号',
score TINYINT UNSIGNED COMMENT '分数'
)ENGINE=INNODB;

INSERT `level`(score) VALUES(90), (80), (70);

SELECT * FROM user1 WHERE depId IN (1, 2, 3, 4);

SELECT * FROM user1 
WHERE depId IN (SELECT id FROM dep);

SELECT id, username, score FROM stu
WHERE score >= (SELECT score FROM `level` WHERE id = 1);

SELECT * FROM stu WHERE EXISTS (SELECT score FROM `level` WHERE id = 1);

-- ANY SOME ALL
SELECT * FROM stu WHERE score >= ANY(SELECT score FROM `level`);
SELECT * FROM stu WHERE score > SOME(SELECT score FROM `level`);
SELECT * FROM stu WHERE score > ALL(SELECT score FROM `level`);

-- 创建一个user3表，将表stu中的id, username的信息写入user3中
CREATE TABLE user3(
id INT UNSIGNED AUTO_INCREMENT KEY,
username VARCHAR(20)
) SELECT id, username FROM stu;

-- 将user1表中的username信息插入到user3中
INSERT user3(username) SELECT username FROM user1;

SELECT 字段名称，… FROM 表名1
UNION
SELECT 字段名称，… FROM 表名2;

SELECT 字段名称，… FROM 表名1
UNION ALL 
SELECT 字段名称，… FROM 表名2;

-- 创建表cate
CREATE TABLE cate(
id SMALLINT UNSIGNED AUTO_INCREMENT KEY COMMENT '编号',
cateName VARCHAR(100) NOT NULL UNIQUE COMMENT '分类名称',
pId SMALLINT UNSIGNED NOT NULL DEFAULT 0 COMMENT '父id'
);

-- 插入顶级分类
INSERT cate(cateName, pId) VALUES('服装', 0),
('数码', 0),
('玩具', 0),
-- 插入服装的子分类
('男装', 1),
('女装', 1),
('内衣', 1),  
-- 插入数码的子分类
('电视', 2),
('冰箱', 2),
('洗衣机', 2),
-- 插入玩具的子分类
('爱马仕', 3),
('LV', 3),
('GUCCI', 3),
-- 插入男装的子分类
('夹克', 4),
('衬衫', 4),
('裤子', 4),
-- 插入电视的子分类
('液晶电视', 7),
('等离子电视', 7),
('背投电视', 7);

-- 查询所有的分类信息，并且得到其父分类
SELECT s.id, s.cateName AS sCateName, p.cateName AS pCateName
FROM cate AS s
LEFT JOIN cate AS p
ON s.pId = p.id;