在MySQL语句或PHP代码中执行简单的算术 [英] Performing simple arithmetic in MySQL statement or in PHP code

问题描述

例如，假设我有一个包含两个整数列start和end的数据结构，但是我实际上对起始值和起始值与结束值之间的差异感兴趣.

For instance, say I have a data structure with two integer columns start and end, but I'm actually interested in the start and difference between start and end values.

我可以发送此查询:

SELECT start, end - start FROM foo;

或者，我可以做

SELECT start, end FROM foo;

并在PHP中执行$end - $start操作.将这些简单的操作留给MySQL更好吗?

and perform the $end - $start operation in PHP. Is it better to leave these sorts of simple operations to MySQL?

推荐答案

我将"$ end-$ start"分类为业务逻辑，并且属于模型层而不是持久层.这意味着要在PHP中执行计算.这有很多好处:

I would classify "$end - $start" as business logic, and that belongs in the model layer not the persistence layer. That means performing the calculation in PHP. This has a number of benefits:

• 如果以后更改数据库，则不需要相同的运算符.

• If you change databases later, you don't need the same operators to exist.

您可以控制执行计算的逻辑.

You can source control the logic that performs the calculation.

您可以更彻底地进行单元测试.

You can more thoroughly unit test.

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