mysql字符串转换返回0 [英] mysql string conversion return 0
问题描述
为什么select 'aaa' =0返回1(TRUE)
如果我有一张桌子
why select 'aaa' =0 return 1 (TRUE)
if i have a table like
userid | pass
user1 | pas1
如果我查询:
select from table where userid = 0 and pass =0
它给了我所有的行吗?
推荐答案
MySQL看到'aaa'= 0并自省:
MySQL sees 'aaa' = 0 and thinks to itself:
我可以将aaa转换为整数，也可以将0转换为字符串."
"I can either convert aaa to an integer, or 0 to a string."
猜猜它是哪一个?
基本上发生的是'aaa'正在转换为整数，并且由于它不是有效的整数，所以将其强制转换为0.
Basically what's happening is that 'aaa' is being converting to an integer, and as it's not a valid integer, it casts to 0.
0 = 0当然是正确的(或true == 1).
0 = 0 is of course true (or true == 1).
我怀疑您的userid列也发生了同样的事情，尽管不知道其值/数据类型，这很难说.
I suspect the same is happening with your userid column, though without knowing its values/datatype, it's hard to say.
http://dev.mysql.com/doc/refman/5.0/en/type-conversion.html
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