MySQL自动将字符串转换/转换为数字? [英] MySQL automatically cast/convert a string to a number?

问题描述

MySQL是否自动将字符串强制转换\转换为数字值?
转换如何进行?

Does MySQL automatically casting\converting the string to numeric value?
How does that conversion works?

• '1234'= 1234吗?
• '1abc'= 1吗?
• 文字" = 1吗?

鉴于units.id是bigint类型，该查询将如何解释?

Given that units.id is of bigint type, how this query will be interpreted?

SELECT table.* 
FROM table 
WHERE id='text'

推荐答案

前三个问题的答案是:是，是和否.

The answers to your first three questions are: yes, yes, and no.

当字符串'text'转换为数字时，它将变为值0.

When the string 'text' is converted to a number, it becomes the value 0.

描述类型转换的文档位于此处

The documentation that describes type conversion is here.

对于您的查询:

SELECT table.* 
FROM table 
WHERE id='text';

此摘录摘自文档中的规则:

The rule is captured by this excerpt from the documentation:

在所有其他情况下，将参数作为浮点数(实数)进行比较.

In all other cases, the arguments are compared as floating-point (real) numbers.

换句话说，这实际上等效于:

In other words, this is actually equivalent to:

WHERE id = 0.0

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