修改(Update)

语法:

UPDATE table_name SET column = expr [, column = expr ...][WHERE ...] [ORDER BY ...] [LIMIT ...]

SQL语句
update 表名 set 列名= 修改后的值 where 条件;

案例:

-- 将孙悟空同学的数学成绩变更为 80 分UPDATE exam_result SET math = 80 WHERE name = '孙悟空';-- 将曹孟德同学的数学成绩变更为 60 分，语文成绩变更为 70 分UPDATE exam_result SET math = 60, chinese = 70 WHERE name = '曹孟德';-- 将总成绩倒数前三的 3 位同学的英语成绩加上 30 分UPDATE exam_result SET math = math + 30 ORDER BY chinese + math + english LIMIT3;-- 将所有同学的语文成绩更新为原来的 2分之一UPDATE exam_result SET chinese = chinese /2;

删除（Delete）

SQL语句
delete from 表名 where 条件;

-- 删除孙悟空同学的考试成绩DELETE FROM exam_result WHERE name = '孙悟空';-- 删除整张表数据-- 准备测试表DROP TABLE IF EXISTS for_delete;CREATE TABLE for_delete (id INT,name VARCHAR(20));-- 插入测试数据INSERT INTO for_delete (name) VALUES ('A'), ('B'), ('C');-- 删除整表数据DELETE FROM for_delete;