Question

我正在尝试列出一年中每个月的数据库中最好的租借书籍。我正在尝试列出最多10本书，并列出最多的租金，例如

十二月|书名| 3份副本
十二月|书名| 2份
十二月|书名| 1份
十一月|书名| 2份
十一月|书名| 1份
十月|书名| 2份

目前它是随机输出但按月分组。我将附上我的架构以及我的查询。

查询

        USE data_mart;
        SELECT bookId, book_name, COUNT(*) AS 'Rental Count', month(rental_date) as 'Month'
        FROM fact_rental
        GROUP BY month(rental_date), bookId
        ORDER BY month(rental_date) DESC;

模式

CREATE TABLE fact_rental (
  rental_id INT(8) UNSIGNED AUTO_INCREMENT,
  cardNo int(11) NOT NULL,
  borrower_fname varchar(45) DEFAULT NULL,
  borrower_lname varchar(45) DEFAULT NULL,
  staffNo int(11) NOT NULL,
  staff_fname varchar(45) DEFAULT NULL,
  staff_lname varchar(45) DEFAULT NULL,
  branchId int(11) NOT NULL,
  branchName varchar(45) DEFAULT NULL,
  bookId int(11) NOT NULL,
  book_name varchar(45) DEFAULT NULL,
  rental_date DATETIME,
  return_date DATETIME DEFAULT NULL,
  count_returns INTEGER(10) DEFAULT 1,
  count_rentals INTEGER(8) UNSIGNED DEFAULT 1,
  FOREIGN KEY (staffNo) REFERENCES dim_staff(staffNo),
  FOREIGN KEY (branchId) REFERENCES dim_library_branch(branchId),
  FOREIGN KEY (cardNo) REFERENCES dim_borrower(cardNo),
  FOREIGN KEY (bookId) REFERENCES dim_book(bookId),
  PRIMARY KEY (rental_id) 
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

Answer 1

你似乎想要：

SELECT bookId, book_name, COUNT(*) AS RentalCount, month(rental_date) as Month
FROM fact_rental
GROUP BY month(rental_date), bookId
ORDER BY RentalCount DESC
LIMIT 10;

Answer 2

对于前10个你可以使用限制10

    USE data_mart;
    SELECT bookId, book_name, COUNT(*) AS 'Rental Count', month(rental_date) as 'Month'
    FROM fact_rental
    GROUP BY month(rental_date), bookId
    ORDER BY month(rental_date) DESC limit 10;

但事实上几个月是递归的..你应该检查（或过滤）一年，例如：

    USE data_mart;
    SELECT bookId, book_name, COUNT(*) AS 'Rental Count', month(rental_date) as 'Month'
    FROM fact_rental
    GROUP BY month(rental_date), bookId
    where year(rental_date) = 2017
    ORDER BY month(rental_date) DESC limit 10;

Answer 3

可能有一种方法，但如果数据集很大，它可能会使数据库服务器崩溃。这个很不理想，但有一个12件UNION你可以得到想要的结果（我按月过滤了一年）：

(SELECT bookId, book_name, COUNT(*) AS rental_count, DATE_FORMAT(rental_date, '%M') as rental_month FROM fact_rental WHERE date_format(rental_date, '%Y-%m') = '2017-10' GROUP BY bookId ORDER BY rental_count DESC LIMIT 10)
UNION ALL
(SELECT bookId, book_name, COUNT(*) AS rental_count, DATE_FORMAT(rental_date, '%M') as rental_month FROM fact_rental WHERE date_format(rental_date, '%Y-%m') = '2017-09' GROUP BY bookId ORDER BY rental_count DESC LIMIT 10)
UNION ALL
(...)

MYSQL按日期按组排序

3 个答案: