python面试题实战（一）

SQL基础

题一：

SELECT author.name,GROUP_CONCAT(book.bookname, book.press) FROM author INNER JOIN(
    book ON author.authorID=book.authorID HAVING author.age<AVG(author.age)
)

题二：

DELETE FROM book WHERE bookID IN(SELECT bookID FROM(SELECT bookID FROM book WHERE bookID IN(SELECT bookID FROM (SELECT bookname,GROUP_CONCAT(bookID) FROM book GROUP BY bookname,authorID HAVING COUNT(*)>1)AS A)AND bookID NOT IN(SELECT MIN(bookID) FROM(SELECT bookname,GROUP_CONCAT(bookID) FROM book GROUP BY bookname,authorID HAVING COUNT(*)>1)AS B))AS S);

题三：

cd 到某个目录
cd ..  返回上一层
ls  查看内容
tree 显示文件和目录有跟结构开始的树结构
mkdir dir1 创建目录
rm -f file1  删除文件1
rmdir dir1  删除目录
shutdown -