自动递增 - 每年自动重置

问题描述

MySQL/InnoDB

MySQL/InnoDB

就我而言，我的收据应按年计算；1/2015、2/2015 ... 556/2015 等等.明年来的时候，柜台要重新从1开始，收据应该算为1/2016, 2/2016 ...

In my case my receipts should be counted on yearly basis; 1/2015, 2/2015 ... 556/2015 and so on. When next year comes, the counter should start from 1 again and receipts should be counted as 1/2016, 2/2016 ...

如何定义每年自动重置的 auto_increment 字段?

How to define auto_increment field which will reset itself on yearly basis?

RCID | RCNO | RCYEAR | ...
=====+======+========+====
 200 |    1 |   2015 |
 201 |    2 |   2015 |
 ... |  ... |   2015 |     
 756 |  556 |   2015 |     <- last receipt in 2015
 757 |    1 |   2016 |     <- yearly counter restarted

注意:RCID 是标准的 PK 自动递增字段.

NOTE: RCID is standard PK auto incremented field.

推荐答案

在@RickJames 的帮助下，解决方案是:

After help from @RickJames the solution is:

CREATE TRIGGER ReceiptNumber BEFORE INSERT ON receipts FOR EACH ROW
BEGIN
  SET NEW.rcyear=YEAR(NOW());
  SET NEW.rcno=(SELECT IFNULL(MAX(rcno),0)+1 FROM receipts WHERE rcyear=YEAR(NOW()));
END;

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