那么，对于 mysql，为什么彼此不相等的事物会彼此相等？例如，为什么...
mysql> SELECT '3' = 3;
+---------+
| '3' = 3 |
+---------+
| 1 |
+---------+
只是，为什么？
更重要的是......
mysql> SELECT 0 = '';
+--------+
| 0 = '' |
+--------+
| 1 |
+--------+
但是，为什么？
还有……
mysql> SELECT '3x' into @foo;
Query OK, 1 row affected (0.00 sec)
mysql> SELECT @foo, CAST(@foo as signed), @foo = CAST(@foo as signed);
+------+----------------------+-----------------------------+
| @foo | CAST(@foo as signed) | @foo = CAST(@foo as signed) |
+------+----------------------+-----------------------------+
| 3x | 3 | 1 |
+------+----------------------+-----------------------------+
亲爱的上帝，为什么？
但更糟糕的是......
mysql> SELECT '3x', CAST('3z' as signed), '3x' = CAST('3z' as signed);
+----+----------------------+-----------------------------+
| 3x | CAST('3z' as signed) | '3x' = CAST('3z' as signed) |
+----+----------------------+-----------------------------+
| 3x | 3 | 1 |
+----+----------------------+-----------------------------+
为什么，哦，为什么？为什么它让我哭得这么......？
最佳答案
文档里都有:
http://dev.mysql.com/doc/refman/5.1/en/type-conversion.html
尤其是行
In all other cases, the arguments are compared as floating-point (real) numbers.
所以你所有的比较都是浮点比较，因此非常有意义。
人们可以争论自动类型转换是否有意义(是否可以将 '1' 与 1 进行比较？)...
关于mysql - 为什么是 MySQL ... 为什么？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/23632896/