PHP-检测由于违反唯一约束而导致的MySQL更新/插入失败 [英] PHP - detect mysql update/insertion failure due to violated unique constraint

问题描述

这有点类似于此问题:

PHP MySQL INSERT由于唯一约束而失败

但是我有不同的想法.假设我有一个只有一列的表.该列的名称为标题"，并具有唯一的约束.

but I have a different twist. Let's say I have a table with only one column. The column's name is "title" and it has a unique constraint placed on it.

首先，我在标题="something"的位置插入一行.下次我尝试插入某物"时，它将由于唯一的键约束而失败(这很好).我想做的是让它失败，并检查mysql提供的错误代码，以确保由于唯一键约束而失败. (即，让数据库处理唯一性，而我只处理错误代码，并在结果返回时告诉用户标题已经存在).

First I insert a row where title = "something". The next time I try to insert "something" it will fail due to a unique key constraint (which is good). What I'd like to do is allow it to fail, and check the error code provided by mysql to ensure it failed due to a unique key constraint. (i.e. let the database handle the uniqueness, and I just handle the error code and tell the user that title already exists when the result comes back).

有没有办法做到这一点?

Is there a way to do this?

推荐答案

http://dev.mysql.com/doc/refman/5.5/en/error-messages-server.html

http://php.net/manual/en/function.mysql -errno.php

过去我不得不这样做，这并不有趣:

I've had to do this in the past, and it's not fun:

if( mysql_errno() == 1062) {
    // Duplicate key
} else {
    // ZOMGFAILURE
}

关于编程风格的说明(来自魔术数字.相反，您可以将已知的错误代码(1062)分配给常量(例如MYSQL_CODE_DUPLICATE_KEY).这将使您的代码更易于维护，因为if语句中的条件在内存中逐渐消失后的几个月内仍可读取:)

A note on programming style (Credits to jensgram from this answer)
You should always seek to avoid the use of magic numbers. Instead, you could assign the known error code (1062) to a constant (e.g. MYSQL_CODE_DUPLICATE_KEY). This will make your code easier to maintain as the condition in the if statement is still readable in a few months when the meaning of 1062 has faded from memory :)

这篇关于PHP-检测由于违反唯一约束而导致的MySQL更新/插入失败的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！