MySQL列= 0传回true [英] MySQL column = 0 returns true

问题描述

TL/DR: 我运行此查询= "Select * from test where id = 0"，它返回所有行.

TL/DR: I run this query = "Select * from test where id = 0" and it returns all the rows.

这是我的下面的代码:

 CREATE TABLE IF NOT EXISTS `test` (
   `id` varchar(20) NOT NULL,
   `desc` varchar(100) NOT NULL,
   UNIQUE KEY `id` (`id`)
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1;

 INSERT INTO `test` (`id`, `desc`) VALUES
 ('AA', 'AA Desc'),
 ('BB', 'BB Desc');

  SELECT count(*) FROM test WHERE id = 0

在我看来，它应该不返回任何行，但是它返回表中的所有行.我想念什么吗?任何帮助和解释将是最欢迎的.

In my mind it should return no rows however it returns all the rows in the table. Am I missing something? Any help and explanation would be most welcome.

推荐答案

您正在对文本字段进行算术比较. MySQL会将ID列中的值强制转换为数字值并将其与零进行比较. AA，当被强制时，等于零.

You're performing an arithmetic comparison on a text field. MySQL will coerce the values in your ID column to a numeric value and compare it with zero. AA, when coerced, equals zero.

这篇关于MySQL列= 0传回true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！