SQL关系数据库，用于跟踪全年的销售情况

Question

I am a noobie to relational databases and MySQL. I was tasked with creating an application that can track sales throughout the year down to the day. So as an employee makes a sale, the sale amount and day the sale was made are kept in a database.

This database needs to keep the current sales for the day, the week, the month and the year. It also needs to track what employee those sales belong to and how many sales that employee made on a given day.

I have drawn a database diagram and have built the tables in MySQL. The issue I am having is I heard (through online tutorials and such) that a many to many or junction table is not supposed to have duplication.

Well my junction table would be my sales table. It has a many to 1 with the employee that made the sale and a many to 1 with the sales made that day. So employee1 makes 3 sales on one day, my sales table would look like this:

sale_id | sale_amount | day_id | employee_id
1         500           1        1
2         600           1        1
3         750           1        1

where the day_id is the current day and the employee_id is employee1. Question 1, is this bad, and if so what would be a better solution?

Question 2, what is the best way to determine the day/week/month of a year to keep track of all this data? Manually entering 7 day for each week, 52 weeks for each year, and 12 months for each year seems overly tedious. I entered in 5 years, I then entered 12 months for the first year, 52 weeks for the first year, then stopped before adding days to come here and see if there was a better solution available.

Any help on this would be greatly appreciated. Also I would like to do this without any additional 3rd party software if possible.

Any help is greatly appreciated!

Answer 1

Instead of having the table for days, weeks, months and years, store the date as a datetime type. You will only need two tables.

Employee Table :

DROP TABLE IF EXISTS `employees`;

CREATE TABLE IF NOT EXISTS `tablename` (
    `emp_id`        INT(11) UNSIGNED        NOT NULL    AUTO_INCREMENT                  COMMENT 'Primary Key',
    `emp_name`      VARCHAR(200)            NOT NULL    DEFAULT ''                      COMMENT 'Name of employee',
    `emp_email`     VARCHAR(200)            NOT NULL    DEFAULT ''                      COMMENT 'Email address of employee',
    `emp_password`  VARCHAR(200)            NOT NULL    DEFAULT ''                      COMMENT 'Password encoded',
    PRIMARY KEY (`emp_id`),
    UNIQUE `idx_emp_name` (`emp_name`),
    UNIQUE `idx_emp_email` (`emp_email`)
) 
    ENGINE=MyISAM 
    AUTO_INCREMENT=1 
    DEFAULT CHARSET=utf8 
    COLLATE=utf8_unicode_ci
    COMMENT 'List of Employees';

Sales Table :

DROP TABLE IF EXISTS `sales`;

CREATE TABLE IF NOT EXISTS `tablename` (
    `sale_id`           INT(11) UNSIGNED        NOT NULL    AUTO_INCREMENT                  COMMENT 'Primary Key',
    `sale_amount`       DOUBLE                  NOT NULL    DEFAULT 0                       COMMENT 'Amount Of Sale',
    `sale_date`         DATETIME                NOT NULL    DEFAULT '0000-00-00'            COMMENT 'Date/Time of sale',
    `sale_emp_id`       INT(11)                 NOT NULL                                    COMMENT 'FK To employees',
    PRIMARY KEY (`sale_id`),
    KEY `idx_sale_date` (`sale_date`),
    KEY `idx_sale_emp_id` (`sale_emp_id`)
) 
    ENGINE=MyISAM 
    AUTO_INCREMENT=1 
    DEFAULT CHARSET=utf8 
    COLLATE=utf8_unicode_ci
    COMMENT 'List of Employees';

-- ==============================================================================================
-- TRIGGER: Update sale_date timestamp on sales
-- ==============================================================================================
DELIMITER |

DROP TRIGGER IF EXISTS `sales_CreatedTS`|

CREATE TRIGGER `sales_CreatedTS` BEFORE INSERT ON `sales`
FOR EACH ROW
BEGIN
    SET NEW.`sale_date` = CURRENT_TIMESTAMP;
END|

DELIMITER ;

From these tables you can produce any report by any period type you need.

For instance, you could produce a report by employee and week, with subtotals, like this:

SELECT
    a.`emp_name`,
    WEEK(b.`sale_date`) as `week_no`,
    SUM(b.`sale_amount`) as `total_sales_for_week`
FROM `employees` a
JOIN `sales` b
    ON a.`emp_id` = b.`sales_emp_id`
GROUP BY WEEK(b.`sale_date`),a.`emp_id` WITH ROLLUP;

For more info on the MySQL date functions look at this reference . With those functions, you could produce reports by day of week, date, week, month, and year.