MySQL中HEX函数的用法

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MySQL5.5官方参考文档：

HEX(N_or_S)

If N_or_S is a number, returns a string representation of the hexadecimal value of N, where N is a longlong (BIGINT) number. This is equivalent to CONV(N,10,16).

If N_or_S is a string, returns a hexadecimal string representation of N_or_S where each character in N_or_S is converted to two hexadecimal digits. The inverse of this operation is performed by the UNHEX() function.

mysql> SELECT HEX(255);
        -> 'FF'
mysql> SELECT 0x616263;
        -> 'abc'
mysql> SELECT HEX('abc');
        -> 616263

1.HEX(number),如果number不是整数，则在进行运算前将其四舍五入为最接近的整数,然后返回该数的十六进制数值表示形式；

mysql> SELECT HEX(12.34);+------------+| HEX(12.34) |+------------+| C          |+------------+1 row in set (0.00 sec)mysql> SELECT HEX(12.54);+------------+| HEX(12.54) |+------------+| D          |+------------+1 row in set (0.00 sec)

2.如果number是NULL，将返回NULL值；

mysql> SELECT HEX(NULL);+-----------+| HEX(NULL) |+-----------+| NULL      |+-----------+1 row in set (0.00 sec)

3.如果number是一个字符串，则返回number的十六进制字符串表示形式，其中number里的每个字符被转化为两个十六进制数字：

mysql> SELECT HEX('abc');+------------+| HEX('abc') |+------------+| 616263     |+------------+1 row in set (0.00 sec)mysql> SELECT HEX('a');+----------+| HEX('a') |+----------+| 61       |+----------+1 row in set (0.00 sec)mysql> SELECT HEX('我爱你');+---------------+| HEX('我爱你') |+---------------+| CED2B0AEC4E3  |+---------------+

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