MySQL CRUD 增删改查

INSERT/SELECT/UPDATE/DELETE 完整操作 · 难度：入门 · +20XP

CRUD — 数据库四大操作

INSERT — 插入数据

-- 插入单行
INSERT INTO students (name, age, grade) VALUES ("张三", 20, "A");
-- 插入多行（批量插入更高效）
INSERT INTO students (name, age, grade) VALUES ("李四", 22, "B"), ("王五", 21, "A");

SELECT — 查询数据

SELECT * FROM students;                            -- 所有行所有列
SELECT name, age FROM students;                    -- 指定列（推荐）
SELECT DISTINCT grade FROM students;              -- 去重
SELECT * FROM students WHERE grade = "A" LIMIT 5; -- 限制行数

UPDATE — 更新数据

UPDATE students SET grade = "A+" WHERE id = 1;     -- ⚠️ 必须加 WHERE！
UPDATE students SET age = 21, grade = "B+" WHERE name = "张三";

DELETE — 删除数据

DELETE FROM students WHERE id = 10;               -- ⚠️ 必须加 WHERE！
DELETE FROM students WHERE grade = "F";           -- 删除多条

⚠️ UPDATE 和 DELETE 不加 WHERE 会操作全表！生产环境务必小心。