MySQL自动将字符串转换/转换为数字?
MySQL 是否自动将字符串转换为数值?
这种转换是如何工作的?
Does MySQL automatically casting\converting the string to numeric value?
How does that conversion works?
- '1234'=1234 ?
- '1abc' = 1 ?
- 'text' = 1 ?
鉴于 units.id 是 bigint 类型，将如何解释此查询?
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'被转换为数字时，它变成了值0.
When the string 'text' is converted to a number, it becomes the value 0.
描述类型转换的文档在这里.
The documentation that describes type conversion is here.
对于您的查询:
SELECT table.*
FROM table
WHERE id='text';
此规则摘录自文档:
在所有其他情况下，参数作为浮点(实数)数进行比较.
In all other cases, the arguments are compared as floating-point (real) numbers.
换句话说，这实际上相当于:
In other words, this is actually equivalent to:
WHERE id = 0.0
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