从零学SQL——4.修改

关系数据库的基本操作就是增删改查，即CRUD：Create、Retrieve、Update、Delete。
增、删、改，对应的SQL语句分别是：

1. INSERT：插入新记录；
2. UPDATE：更新已有记录；
3. DELETE：删除已有记录。

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• INSETR

INSERT INTO students (class_id, name, gender, score) VALUES
  (1, '大宝', 'M', 87),
  (2, '二宝', 'M', 81);

SELECT * FROM students;

UPDATE students SET name='小牛', score=77 WHERE id>=5 AND id<=7;
-- 查询并观察结果:
SELECT * FROM students;

UPDATE students SET score=score+10 WHERE score<80;
-- 查询并观察结果:
SELECT * FROM students;

DELETE FROM students WHERE id>=5 AND id<=7;
-- 查询并观察结果:
SELECT * FROM students;

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