sql语句执行顺序
FROM/JOIN → WHERE → GROUP BY → HAVING → 窗口函数(OVER) → SELECT → DISTINCT → ORDER BY → LIMIT
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简单的用法
1. 数据库操作
- 创建数据库
create database db1; - 使用数据库
use db1;
2.数据定义DDL:create,drop,alter
- 创建表
create table t1 (id int primary key, name varchar(20)...); - 修改表
alter table t1 add column id int;
alter table t1 modify column id varchar(20);
alter table t1 drop column name;
alter table t1 rename to t2; - 查看表
desc t1;-- 查看表结构
show tables;-- 查看所有表
3.数据操纵DML:insert，update
- 插入数据
--插入多条数据
INSERT INTO user (name, age, email) VALUES ('张三', 25, 'zhangsan@test.com'),('李四', 30, 'lisi@test.com'); --插入全部信息
INSERT INTO user VALUES (3, '王五', 28, 'wangwu@test.com', '2026-01-26 10:00:00');
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修改数据
UPDATE user SET age = 26, email = 'zhangsan_new@test.com' WHERE id = 1; -
删除数据
DELETE FROM user WHERE id = 3;
truncate table t1; -- 清空表及相关信息
