Sql语法学习
- 创建表示例:
CREATE TABLE students (
id INT PRIMARY KEY,
name VARCHAR(100),
age INT,
grade VARCHAR(10)
);
- 插入数据示例:
INSERT INTO students (id, name, age, grade)
VALUES (1, ‘John’, 18, ‘A’);
INSERT INTO students (id, name, age, grade)
VALUES (2, ‘Jane’, 19, ‘B’);
- 更新数据示例:
UPDATE students
SET age = 20
WHERE id = 1;
- 删除数据示例:
DELETE FROM students
WHERE id = 2;
- 查询数据示例:
SELECT * FROM students;
SELECT name, age FROM students
WHERE grade = ‘A’;
- 使用聚合函数示例:
SELECT COUNT(*) FROM students;
SELECT AVG(age) FROM students
WHERE grade = ‘A’;
- 使用JOIN示例:
SELECT students.name, courses.course_name
FROM students
JOIN courses ON students.id = courses.student_id;
- 使用子查询示例:
SELECT name
FROM students
WHERE age <= (SELECT AVG(age) FROM students);
- 使用ORDER BY排序示例:
SELECT * FROM students
ORDER BY age DESC;
- 使用LIMIT限制查询结果示例:
SELECT * FROM students
LIMIT 5;
这只是一些常见的SQL语法示例,SQL语言非常强大且灵活,可以根据需求进行更多的操作和组合。
原文地址:https://blog.csdn.net/qq_33570734/article/details/142564807
免责声明:本站文章内容转载自网络资源,如本站内容侵犯了原著者的合法权益,可联系本站删除。更多内容请关注自学内容网(zxcms.com)!