Question

我试图让这张桌子显示书籍数量，书名，以及每本书被检出的次数（即使它从未被检出过。）

我得到的当前输出是正确的，但我想按书号和“时间检出”对其进行排序。

SELECT book.book_num
  ,book_title
  ,Count(checkout.book_num) AS "Times Checked Out"
FROM checkout right join book ON checkout.book_num = book.book_num
GROUP BY book.book_num, book_title;

Answer 1

您也可以将其用作内部查询：

SELECT * FROM (
    SELECT book.book_num,book_title,Count(checkout.book_num) AS "Times Checked Out"
    FROM checkout right join book ON checkout.book_num = book.book_num
    GROUP BY book.book_num, book_title
) AS foo
ORDER BY "Times Checked Out";

Answer 2

SELECT
    book.book_num,
    book_title,
    COUNT(checkout.book_num) AS "Times Checked Out"
FROM checkout
RIGHT JOIN book ON checkout.book_num = book.book_num 
GROUP BY
    book.book_num,
    book_title
ORDER BY
    book.book_num,
    COUNT(checkout.book_num);

Answer 3

使用公用表表达式

;WITH BookDetails AS
(
    SELECT book.book_num
          ,book_title
          ,Count(checkout.book_num) AS "TimesCheckedOut"
    FROM checkout right join book ON checkout.book_num = book.book_num
    GROUP BY book.book_num, book_title;
)

SELECT
    book_num
   ,book_title
   ,TimesCheckedOut as 'Times Checked Out'
FROM BookDetails
ORDER BY TimesCheckedOut

这假设您没有使用MySql，而是使用类似MSSQL

的东西

Answer 4

最简单的方法是将其设置为子查询并对其进行排序：

SELECT book_num AS "Book Number",
 ,book_title AS "Book Title"
 ,times_checked_out AS "Times Checked Out"
FROM (
    SELECT Book.book_num
      ,Book.book_title
      ,COUNT(Checkout.book_num) AS times_checked_out
    FROM checkout Checkout
    RIGHT OUTER JOIN book Book ON Checkout.book_num = Book.book_num
    GROUP BY Book.book_num, Book.book_title
) Counts
ORDER BY book_num,times_checked_out

这只会执行COUNT一次，并提供您正在寻找的订单。它也符合ANSI标准，非常高效。

需要帮助排序表与聚合函数

4 个答案: