本教程为常用SQL语句的汇总,我把他放到了码云上面,项目地址:https://gitee.com/love-code-bear/java/blob/master/SQL.md
SHOW DATABASES;
CREATE DATABASE db2;
CREATE DATABASE IF NOT EXISTS db2;
DROP DATABASE db2;
drop DATABASE IF EXISTS db2;
– 查看当前所使用的数据库
SELECT DATABASE();
use db1;
CREATE TABLE jd_user(
id int,
username VARCHAR(32),
password VARCHAR(32)
);
DESC stu;
USE DATABASE db1;
SHOW TABLES;
DROP TABLE tb_user;
DROP TABLE IF EXISTS tb_user;
ALTER TABLE jd_user ADD address VARCHAR(32);
ALTER TABLE jd_user RENAME TO jd_user;
ALTER TABLE jd_user MODIFY address CHAR(32);
DESC jd_user;
ALTER TABLE jd_user CHANGE address location VARCHAR(64);
1.4.5 查询所有数据
SELECT * FROM jd_user;
SELECT * FROM stu;
alter table stu change name name varchar(255) character set utf8;
INSERT INTO stu(id,name) VALUES(1,'张三');
alter table stu change sex sex varchar(255) character set utf8;
INSERT INTO stu(id,name,sex,birthday,score,email,tel,status) VALUES
(2,'lisa','女','1999-11-11',98.00,'[email protected]',1123,1);
INSERT INTO stu VALUES(3,'小米','男','1998-10-17',93.00,'[email protected]',1433,1);
INSERT INTO stu VALUES
(4,'huawei','男','1998-10-17',93.00,'[email protected]',1433,1),
(5,'荣耀','男','1998-10-17',93.00,'[email protected]',1433,1),
(6,'苹果','男','1998-10-17',93.00,'[email protected]',1433,1);
UPDATE stu SET sex = '男' WHERE name = '张三';
UPDATE stu SET birthday = '2000-02-28',score = '99.00' WHERE name = '张三';
DELETE FROM stu WHERE name = '小米';
– 使用数据库
USE db1;
– 创建表
CREATE TABLE stu1 (
id int,
name VARCHAR(32),
age int,
sex VARCHAR(4),
address VARCHAR(64),
math DOUBLE(5,2),
english DOUBLE(5,2),
hire_date DATE
);
– 插入数据
ALTER TABLE stu1 CHANGE name name VARCHAR(32) character set utf8;
ALTER TABLE stu1 CHANGE sex sex VARCHAR(4) character set utf8;
ALTER TABLE stu1 CHANGE address address VARCHAR(64) character set utf8;
INSERT INTO stu1(id,name,age,sex,address,math,english,hire_date)
VALUES
(1,'张一',25,'男','杭州',66.00,78.00,'1998-09-09'),
(2,'张二',24,'女','北京',87.00,76.00,'1996-09-09'),
(3,'张三',22,'男','郑州',94.00,65.00,'1997-09-09'),
(4,'张四',23,'男','合肥',69.00,75.00,'1998-09-09'),
(5,'张五',23,'女','无锡',76.00,79.00,'1999-09-09'),
(6,'张六',24,'女','苏州',88.00,94.00,'1998-03-09'),
(7,'张七',21,'男','南通',89.00,90.00,'1998-05-09'),
(8,'张八',22,'男','南充',98.00,90.00,'1998-07-09');
– 查询所有数据
SELECT * FROM stu1;
USE db1;
SELECT *FROM stu1;
SELECT `name`,age,sex,address,math,english,hire_date FROM stu1;
SELECT `name`,age FROM stu1;
SELECT english FROM stu1;
SELECT DISTINCT english FROM stu1;
SELECT name AS 姓名,math AS 数学,english AS 英语 FROM stu1;
SELECT * FROM stu1 WHERE age > 23;
SELECT * FROM stu1 WHERE age >= 24;
SELECT * FROM stu1 WHERE age>=21 AND age <= 23;
SELECT * FROM stu1 WHERE age BETWEEN 21 AND 23;
SELECT * FROM stu1 WHERE hire_date BETWEEN '1997-05-09' AND '1998-07-09';
SELECT * FROM stu1 WHERE age = 21;
SELECT * FROM stu1 WHERE age = 21 OR age = 24 OR age = 25;
SELECT * FROM stu1 WHERE age IN(21,24,25);
SELECT * FROM stu1 WHERE english IS NOT null;
SELECT * FROM stu1 WHERE `name` LIKE '张%';
-- 查询第二个字是'三'的学员信息
SELECT * FROM stu1 WHERE `name` LIKE '_三%';
-- 查询名字中含有'四'的学员信息
SELECT * FROM stu1 WHERE `name` LIKE '%四%';
SELECT * FROM stu1 ORDER BY age ASC;
SELECT * FROM stu1 ORDER BY math DESC;
SELECT * FROM stu1 ORDER BY english DESC , math ASC;
SELECT COUNT(id) FROM stu1;
SELECT COUNT(*) FROM stu1;
SELECT MAX(math) FROM stu1;
SELECT MIN(math) FROM stu1;
SELECT SUM(math) FROM stu1;
SELECT AVG(math) FROM stu1;
SELECT sex,AVG(math) FROM stu1 GROUP BY sex;
SELECT sex,AVG(math),COUNT(*) FROM stu1 GROUP BY sex;
SELECT sex,AVG(math),COUNT(*) FROM stu1 WHERE math > 80 GROUP BY sex;
SELECT sex,AVG(math),COUNT(*) FROM stu1 WHERE math > 80 GROUP BY sex HAVING COUNT(*) > 2;
SELECT * FROM stu1;
SELECT * FROM stu1 LIMIT 0,3;
SELECT * FROM stu1 LIMIT 0,3;
SELECT * FROM stu1 LIMIT 3,3;
SELECT * FROM stu1 LIMIT 6,3;
SELECT * FROM stu1 LIMIT 4,4;
-- 员工表
CREATE TABLE emp(
id INT PRIMARY KEY,/*员工id主键,且自增长*/
ename VARCHAR(32) UNIQUE,/*员工姓名,非空且唯一*/
joindate DATE NOT NULL,/*入职日期非空*/
salary DOUBLE(7,2) NOT NULL,/*薪水,非空*/
bonus DOUBLE(7,2) DEFAULT 0/*奖金,默认为0*/
);
DESC emp;
ALTER TABLE emp CHANGE ename ename VARCHAR(32) CHARACTER set utf8;
INSERT INTO emp(id,ename,joindate,salary,bonus) VALUES(1,'张三','1999-11-11',8800,5000);
SELECT * FROM emp;
INSERT INTO emp(id,ename,joindate,salary,bonus) VALUES(NULL,'张三','1999-11-11',8800,5000);
INSERT INTO emp(id,ename,joindate,salary,bonus) VALUES(1,'张三','1999-11-11',8800,5000);
INSERT INTO emp(id,ename,joindate,salary,bonus) VALUES(2,'李四','1999-11-11',8800,5000);
DELETE FROM emp WHERE id = 3;
INSERT INTO emp(id,ename,joindate,salary,bonus) VALUES(3,null,'1999-11-11',8800,5000);
INSERT INTO emp(id,ename,joindate,salary,bonus) VALUES(3,'李四','1999-11-11',8800,5000);
ALTER TABLE emp MODIFY ename VARCHAR(32) CHARACTER set utf8;
ALTER TABLE emp MODIFY ename VARCHAR(32) NOT NULL ;
DESC emp;
DROP TABLE emp;
-- 员工表
CREATE TABLE emp(
id INT PRIMARY KEY auto_increment,/*员工id主键,且自增长*/
name VARCHAR(32),/*员工姓名,非空且唯一*/
age INT,
dep_id INT,/*联系到拎一个表*/
-- 添加一个外键约束
CONSTRAINT fk_emp_dept FOREIGN KEY(dep_id) REFERENCES dept(id)
);
-- 部门表
CREATE TABLE dept(
id INT PRIMARY KEY auto_increment,
dep_name VARCHAR(32),
address VARCHAR(32)
);
DESC emp;
DESC dept;
DROP TABLE emp;
DROP TABLE dept;
ALTER TABLE emp CHANGE name name VARCHAR(32) CHARACTER set utf8;
ALTER TABLE dept CHANGE dep_name dep_name VARCHAR(32) CHARACTER set utf8;
ALTER TABLE dept CHANGE address address VARCHAR(32) CHARACTER set utf8;
INSERT INTO emp (name,age,dep_id) VALUES
('张三',20,1),
('李四',20,1),
('王五',20,1),
('赵六',20,2),
('孙七',22,2),
('周八',18,2);
INSERT INTO dept (dep_name,address) VALUES
('研发部','广州'),
('销售部','深圳');
SELECT * FROM emp;
SELECT * FROM dept;
-- 删除外键
ALTER TABLE emp DROP FOREIGN KEY fk_emp_dept;
-- 添加外键
ALTER TABLE emp ADD CONSTRAINT fk_emp_dept FOREIGN KEY(dep_id) REFERENCES dept(id);
使用数据库,展示所有表
USE db1;
SHOW TABLES;
-- 订单表
CREATE TABLE tb_order(
id INT PRIMARY KEY auto_increment,
payment double(10,2),
payment_type TINYINT,
status TINYINT
);
-- 商品表
CREATE TABLE tb_goods(
id INT PRIMARY KEY auto_increment,
title VARCHAR(100),
price DOUBLE(10,2)
);
-- 中间表
CREATE TABLE tb_order_goods(
id INT PRIMARY KEY auto_increment,
order_id INT,
goods_id INT
);
-- 添加外键
ALTER TABLE tb_order_goods ADD CONSTRAINT fk_order_id FOREIGN KEY(order_id) REFERENCES tb_order(id);
ALTER TABLE tb_order_goods ADD CONSTRAINT fk_goods_id FOREIGN KEY(goods_id) REFERENCES tb_goods(id);
SHOW TABLES;
-- 用户表
CREATE TABLE tb_user(
id INT PRIMARY KEY auto_increment,
photo VARCHAR(100),
name VARCHAR(32),
age INT,
sex VARCHAR(4),
desc_id INT UNIQUE,
CONSTRAINT tb_user_desc FOREIGN KEY(desc_id) REFERENCES tb_user_desc(id)
);
-- 用户详情表
CREATE TABLE tb_user_desc(
id INT PRIMARY KEY auto_increment,
city VARCHAR(32),
edu VARCHAR(32),
income DOUBLE(7,2),
status TINYINT
);
ALTER TABLE tb_user_desc CHANGE status status VARCHAR(16) CHARACTER set utf8;
INSERT into tb_user_desc(city,edu,income,status) VALUES
('广州','本科',3000,'单身'),
('广州','硕士',12000,'单身');
INSERT into tb_user(photo,`name`,age,sex,desc_id) VALUES
('c盘','林青霞',22,'女',1),
('d盘','风清扬',24,'男',2);
ALTER TABLE tb_user auto_increment = 1;
SELECT * FROM tb_user;
SELECT * FROM tb_user_desc;
DESC tb_user;
DESC tb_user_desc;
DROP TABLE tb_user;
4.1.3 查看所有外键
SELECT * FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE;
-- 音乐专辑表名
CREATE TABLE music(
title VARCHAR(32),/*专辑名*/
alias VARCHAR(32),/*专辑别名*/
image VARCHAR(64),/*封面图片*/
style VARCHAR(16),/*流派(经典、流行、民谣)*/
type VARCHAR(8),/*类型(专辑,单曲)*/
medium VARCHAR(8),/*介质(胶片,cd)*/
publish_time DATE,/*发行时间*/
publisher VARCHAR(8),/*出版者*/
number TINYINT,/*唱片数量*/
barcode BIGINT,/*条形码*/
summary VARCHAR(1024),/*简介*/
artist VARCHAR(32),/*艺术家*/
id INT UNIQUE/*编号,唯一*/
);
-- 曲目表名
CREATE TABLE song(
name VARCHAR(32),/*歌曲名*/
serial_number TINYINT,/*歌曲序号*/
id INT UNIQUE/*编号,唯一*/
);
-- 评论表名
CREATE TABLE review(
content VARCHAR(1024),/*评论内容*/
rating TINYINT,/*评分1-5*/
review datetime,/*评论时间*/
content_user_id INT,
content_music_id INT
);
-- 用户表名
CREATE TABLE user(
username VARCHAR(32),
image VARCHAR(64),
signture VARCHAR(64),
name VARCHAR(32),
id INT PRIMARY KEY
);
-- 展示
DESC music;
DESC song;
DESC review;
DESC user;
-- 删除
DROP TABLE music;
DROP TABLE song;
DROP TABLE review;
DROP TABLE user;
-- 专辑和用户的中间表
CREATE TABLE music_user(
id INT PRIMARY KEY auto_increment,
music_id INT,
user_id INT
);
-- 添加专辑和用户外键
ALTER TABLE music_user ADD CONSTRAINT fk_music_id FOREIGN KEY(music_id) REFERENCES music(id);
ALTER TABLE music_user ADD CONSTRAINT fk_user_id FOREIGN KEY(user_id) REFERENCES user(id);
-- 添加短评和用户外键
ALTER TABLE review ADD CONSTRAINT fk_review_user FOREIGN KEY(content_user_id) REFERENCES user(id);
-- 添加短评专辑外键
ALTER TABLE review ADD CONSTRAINT fk_review_music FOREIGN KEY(content_music_id) REFERENCES music(id);
-- 添加曲目和专辑外键
ALTER TABLE song ADD CONSTRAINT fk_song_music FOREIGN KEY(id) REFERENCES music(id);
ALTER TABLE song DROP FOREIGN KEY fk_song_user;
– 多表查询
SELECT * FROM emp;
SELECT * FROM dept;
SELECT * FROM emp,dept;
– 产生笛卡尔积(有ab两个集合,去a和b所有的组合情况)
– 消除无效数据
– 查询emp和dept的数据,emp.dep_id = dept.id
– 隐式内连接
SELECT * FROM emp,dept WHERE emp.dep_id = dept.id;
– 查询emp的name,age,dept表的dep_name
SELECT emp.`name`,emp.age,dept.dep_name FROM emp,dept WHERE emp.dep_id = dept.id;
– 给表起别名
SELECT t1.`name`,t1.age,t2.dep_name FROM emp AS t1,dept AS t2 WHERE t1.dep_id = t2.id;
– 显式内连接
SELECT * FROM emp LEFT OUTER JOIN dept ON emp.dep_id = dept.id;
SELECT * FROM emp LEFT /*OUTER*/ JOIN dept ON emp.dep_id = dept.id;
– 右外连接
SELECT * FROM emp RIGHT OUTER JOIN dept ON emp.dep_id = dept.id;
SELECT * FROM emp RIGHT /*OUTER*/ JOIN dept ON emp.dep_id = dept.id;
```# 1 DDL
## 1.1 显示所包含的数据库
```mysql
SHOW DATABASES;
CREATE DATABASE db2;
CREATE DATABASE IF NOT EXISTS db2;
DROP DATABASE db2;
drop DATABASE IF EXISTS db2;
– 查看当前所使用的数据库
SELECT DATABASE();
use db1;
CREATE TABLE jd_user(
id int,
username VARCHAR(32),
password VARCHAR(32)
);
DESC stu;
USE DATABASE db1;
SHOW TABLES;
DROP TABLE tb_user;
DROP TABLE IF EXISTS tb_user;
ALTER TABLE jd_user ADD address VARCHAR(32);
ALTER TABLE jd_user RENAME TO jd_user;
ALTER TABLE jd_user MODIFY address CHAR(32);
DESC jd_user;
ALTER TABLE jd_user CHANGE address location VARCHAR(64);
1.4.5 查询所有数据
SELECT * FROM jd_user;
SELECT * FROM stu;
alter table stu change name name varchar(255) character set utf8;
INSERT INTO stu(id,name) VALUES(1,'张三');
alter table stu change sex sex varchar(255) character set utf8;
INSERT INTO stu(id,name,sex,birthday,score,email,tel,status) VALUES
(2,'lisa','女','1999-11-11',98.00,'[email protected]',1123,1);
INSERT INTO stu VALUES(3,'小米','男','1998-10-17',93.00,'[email protected]',1433,1);
INSERT INTO stu VALUES
(4,'huawei','男','1998-10-17',93.00,'[email protected]',1433,1),
(5,'荣耀','男','1998-10-17',93.00,'[email protected]',1433,1),
(6,'苹果','男','1998-10-17',93.00,'[email protected]',1433,1);
UPDATE stu SET sex = '男' WHERE name = '张三';
UPDATE stu SET birthday = '2000-02-28',score = '99.00' WHERE name = '张三';
DELETE FROM stu WHERE name = '小米';
– 使用数据库
USE db1;
– 创建表
CREATE TABLE stu1 (
id int,
name VARCHAR(32),
age int,
sex VARCHAR(4),
address VARCHAR(64),
math DOUBLE(5,2),
english DOUBLE(5,2),
hire_date DATE
);
– 插入数据
ALTER TABLE stu1 CHANGE name name VARCHAR(32) character set utf8;
ALTER TABLE stu1 CHANGE sex sex VARCHAR(4) character set utf8;
ALTER TABLE stu1 CHANGE address address VARCHAR(64) character set utf8;
INSERT INTO stu1(id,name,age,sex,address,math,english,hire_date)
VALUES
(1,'张一',25,'男','杭州',66.00,78.00,'1998-09-09'),
(2,'张二',24,'女','北京',87.00,76.00,'1996-09-09'),
(3,'张三',22,'男','郑州',94.00,65.00,'1997-09-09'),
(4,'张四',23,'男','合肥',69.00,75.00,'1998-09-09'),
(5,'张五',23,'女','无锡',76.00,79.00,'1999-09-09'),
(6,'张六',24,'女','苏州',88.00,94.00,'1998-03-09'),
(7,'张七',21,'男','南通',89.00,90.00,'1998-05-09'),
(8,'张八',22,'男','南充',98.00,90.00,'1998-07-09');
– 查询所有数据
SELECT * FROM stu1;
USE db1;
SELECT *FROM stu1;
SELECT `name`,age,sex,address,math,english,hire_date FROM stu1;
SELECT `name`,age FROM stu1;
SELECT english FROM stu1;
SELECT DISTINCT english FROM stu1;
SELECT name AS 姓名,math AS 数学,english AS 英语 FROM stu1;
SELECT * FROM stu1 WHERE age > 23;
SELECT * FROM stu1 WHERE age >= 24;
SELECT * FROM stu1 WHERE age>=21 AND age <= 23;
SELECT * FROM stu1 WHERE age BETWEEN 21 AND 23;
SELECT * FROM stu1 WHERE hire_date BETWEEN '1997-05-09' AND '1998-07-09';
SELECT * FROM stu1 WHERE age = 21;
SELECT * FROM stu1 WHERE age = 21 OR age = 24 OR age = 25;
SELECT * FROM stu1 WHERE age IN(21,24,25);
SELECT * FROM stu1 WHERE english IS NOT null;
SELECT * FROM stu1 WHERE `name` LIKE '张%';
-- 查询第二个字是'三'的学员信息
SELECT * FROM stu1 WHERE `name` LIKE '_三%';
-- 查询名字中含有'四'的学员信息
SELECT * FROM stu1 WHERE `name` LIKE '%四%';
SELECT * FROM stu1 ORDER BY age ASC;
SELECT * FROM stu1 ORDER BY math DESC;
SELECT * FROM stu1 ORDER BY english DESC , math ASC;
SELECT COUNT(id) FROM stu1;
SELECT COUNT(*) FROM stu1;
SELECT MAX(math) FROM stu1;
SELECT MIN(math) FROM stu1;
SELECT SUM(math) FROM stu1;
SELECT AVG(math) FROM stu1;
SELECT sex,AVG(math) FROM stu1 GROUP BY sex;
SELECT sex,AVG(math),COUNT(*) FROM stu1 GROUP BY sex;
SELECT sex,AVG(math),COUNT(*) FROM stu1 WHERE math > 80 GROUP BY sex;
SELECT sex,AVG(math),COUNT(*) FROM stu1 WHERE math > 80 GROUP BY sex HAVING COUNT(*) > 2;
SELECT * FROM stu1;
SELECT * FROM stu1 LIMIT 0,3;
SELECT * FROM stu1 LIMIT 0,3;
SELECT * FROM stu1 LIMIT 3,3;
SELECT * FROM stu1 LIMIT 6,3;
SELECT * FROM stu1 LIMIT 4,4;
-- 员工表
CREATE TABLE emp(
id INT PRIMARY KEY,/*员工id主键,且自增长*/
ename VARCHAR(32) UNIQUE,/*员工姓名,非空且唯一*/
joindate DATE NOT NULL,/*入职日期非空*/
salary DOUBLE(7,2) NOT NULL,/*薪水,非空*/
bonus DOUBLE(7,2) DEFAULT 0/*奖金,默认为0*/
);
DESC emp;
ALTER TABLE emp CHANGE ename ename VARCHAR(32) CHARACTER set utf8;
INSERT INTO emp(id,ename,joindate,salary,bonus) VALUES(1,'张三','1999-11-11',8800,5000);
SELECT * FROM emp;
INSERT INTO emp(id,ename,joindate,salary,bonus) VALUES(NULL,'张三','1999-11-11',8800,5000);
INSERT INTO emp(id,ename,joindate,salary,bonus) VALUES(1,'张三','1999-11-11',8800,5000);
INSERT INTO emp(id,ename,joindate,salary,bonus) VALUES(2,'李四','1999-11-11',8800,5000);
DELETE FROM emp WHERE id = 3;
INSERT INTO emp(id,ename,joindate,salary,bonus) VALUES(3,null,'1999-11-11',8800,5000);
INSERT INTO emp(id,ename,joindate,salary,bonus) VALUES(3,'李四','1999-11-11',8800,5000);
ALTER TABLE emp MODIFY ename VARCHAR(32) CHARACTER set utf8;
ALTER TABLE emp MODIFY ename VARCHAR(32) NOT NULL ;
DESC emp;
DROP TABLE emp;
-- 员工表
CREATE TABLE emp(
id INT PRIMARY KEY auto_increment,/*员工id主键,且自增长*/
name VARCHAR(32),/*员工姓名,非空且唯一*/
age INT,
dep_id INT,/*联系到拎一个表*/
-- 添加一个外键约束
CONSTRAINT fk_emp_dept FOREIGN KEY(dep_id) REFERENCES dept(id)
);
-- 部门表
CREATE TABLE dept(
id INT PRIMARY KEY auto_increment,
dep_name VARCHAR(32),
address VARCHAR(32)
);
DESC emp;
DESC dept;
DROP TABLE emp;
DROP TABLE dept;
ALTER TABLE emp CHANGE name name VARCHAR(32) CHARACTER set utf8;
ALTER TABLE dept CHANGE dep_name dep_name VARCHAR(32) CHARACTER set utf8;
ALTER TABLE dept CHANGE address address VARCHAR(32) CHARACTER set utf8;
INSERT INTO emp (name,age,dep_id) VALUES
('张三',20,1),
('李四',20,1),
('王五',20,1),
('赵六',20,2),
('孙七',22,2),
('周八',18,2);
INSERT INTO dept (dep_name,address) VALUES
('研发部','广州'),
('销售部','深圳');
SELECT * FROM emp;
SELECT * FROM dept;
-- 删除外键
ALTER TABLE emp DROP FOREIGN KEY fk_emp_dept;
-- 添加外键
ALTER TABLE emp ADD CONSTRAINT fk_emp_dept FOREIGN KEY(dep_id) REFERENCES dept(id);
使用数据库,展示所有表
USE db1;
SHOW TABLES;
-- 订单表
CREATE TABLE tb_order(
id INT PRIMARY KEY auto_increment,
payment double(10,2),
payment_type TINYINT,
status TINYINT
);
-- 商品表
CREATE TABLE tb_goods(
id INT PRIMARY KEY auto_increment,
title VARCHAR(100),
price DOUBLE(10,2)
);
-- 中间表
CREATE TABLE tb_order_goods(
id INT PRIMARY KEY auto_increment,
order_id INT,
goods_id INT
);
-- 添加外键
ALTER TABLE tb_order_goods ADD CONSTRAINT fk_order_id FOREIGN KEY(order_id) REFERENCES tb_order(id);
ALTER TABLE tb_order_goods ADD CONSTRAINT fk_goods_id FOREIGN KEY(goods_id) REFERENCES tb_goods(id);
SHOW TABLES;
-- 用户表
CREATE TABLE tb_user(
id INT PRIMARY KEY auto_increment,
photo VARCHAR(100),
name VARCHAR(32),
age INT,
sex VARCHAR(4),
desc_id INT UNIQUE,
CONSTRAINT tb_user_desc FOREIGN KEY(desc_id) REFERENCES tb_user_desc(id)
);
-- 用户详情表
CREATE TABLE tb_user_desc(
id INT PRIMARY KEY auto_increment,
city VARCHAR(32),
edu VARCHAR(32),
income DOUBLE(7,2),
status TINYINT
);
ALTER TABLE tb_user_desc CHANGE status status VARCHAR(16) CHARACTER set utf8;
INSERT into tb_user_desc(city,edu,income,status) VALUES
('广州','本科',3000,'单身'),
('广州','硕士',12000,'单身');
INSERT into tb_user(photo,`name`,age,sex,desc_id) VALUES
('c盘','林青霞',22,'女',1),
('d盘','风清扬',24,'男',2);
ALTER TABLE tb_user auto_increment = 1;
SELECT * FROM tb_user;
SELECT * FROM tb_user_desc;
DESC tb_user;
DESC tb_user_desc;
DROP TABLE tb_user;
4.1.3 查看所有外键
SELECT * FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE;
-- 音乐专辑表名
CREATE TABLE music(
title VARCHAR(32),/*专辑名*/
alias VARCHAR(32),/*专辑别名*/
image VARCHAR(64),/*封面图片*/
style VARCHAR(16),/*流派(经典、流行、民谣)*/
type VARCHAR(8),/*类型(专辑,单曲)*/
medium VARCHAR(8),/*介质(胶片,cd)*/
publish_time DATE,/*发行时间*/
publisher VARCHAR(8),/*出版者*/
number TINYINT,/*唱片数量*/
barcode BIGINT,/*条形码*/
summary VARCHAR(1024),/*简介*/
artist VARCHAR(32),/*艺术家*/
id INT UNIQUE/*编号,唯一*/
);
-- 曲目表名
CREATE TABLE song(
name VARCHAR(32),/*歌曲名*/
serial_number TINYINT,/*歌曲序号*/
id INT UNIQUE/*编号,唯一*/
);
-- 评论表名
CREATE TABLE review(
content VARCHAR(1024),/*评论内容*/
rating TINYINT,/*评分1-5*/
review datetime,/*评论时间*/
content_user_id INT,
content_music_id INT
);
-- 用户表名
CREATE TABLE user(
username VARCHAR(32),
image VARCHAR(64),
signture VARCHAR(64),
name VARCHAR(32),
id INT PRIMARY KEY
);
-- 展示
DESC music;
DESC song;
DESC review;
DESC user;
-- 删除
DROP TABLE music;
DROP TABLE song;
DROP TABLE review;
DROP TABLE user;
-- 专辑和用户的中间表
CREATE TABLE music_user(
id INT PRIMARY KEY auto_increment,
music_id INT,
user_id INT
);
-- 添加专辑和用户外键
ALTER TABLE music_user ADD CONSTRAINT fk_music_id FOREIGN KEY(music_id) REFERENCES music(id);
ALTER TABLE music_user ADD CONSTRAINT fk_user_id FOREIGN KEY(user_id) REFERENCES user(id);
-- 添加短评和用户外键
ALTER TABLE review ADD CONSTRAINT fk_review_user FOREIGN KEY(content_user_id) REFERENCES user(id);
-- 添加短评专辑外键
ALTER TABLE review ADD CONSTRAINT fk_review_music FOREIGN KEY(content_music_id) REFERENCES music(id);
-- 添加曲目和专辑外键
ALTER TABLE song ADD CONSTRAINT fk_song_music FOREIGN KEY(id) REFERENCES music(id);
ALTER TABLE song DROP FOREIGN KEY fk_song_user;
– 多表查询
SELECT * FROM emp;
SELECT * FROM dept;
SELECT * FROM emp,dept;
– 产生笛卡尔积(有ab两个集合,去a和b所有的组合情况)
– 消除无效数据
– 查询emp和dept的数据,emp.dep_id = dept.id
– 隐式内连接
SELECT * FROM emp,dept WHERE emp.dep_id = dept.id;
– 查询emp的name,age,dept表的dep_name
SELECT emp.`name`,emp.age,dept.dep_name FROM emp,dept WHERE emp.dep_id = dept.id;
– 给表起别名
SELECT t1.`name`,t1.age,t2.dep_name FROM emp AS t1,dept AS t2 WHERE t1.dep_id = t2.id;
– 显式内连接
SELECT * FROM emp LEFT OUTER JOIN dept ON emp.dep_id = dept.id;
SELECT * FROM emp LEFT /*OUTER*/ JOIN dept ON emp.dep_id = dept.id;
– 右外连接
SELECT * FROM emp RIGHT OUTER JOIN dept ON emp.dep_id = dept.id;
SELECT * FROM emp RIGHT /*OUTER*/ JOIN dept ON emp.dep_id = dept.id;
以上就是SQL语句大全的全部内容,希望对你有所帮助。