mysql ORD()函数与ASCII()函数使用分析

ASCII(str1)

返回字符串str的最左面字符的ASCII代码值。如果str是空字符串，返回0。如果str是NULL，返回NULL

举例：

1.

mysql> select ascii(\'hi\');
+————-+
| ascii(\'hi\') |
+————-+
|         104 |
+————-+
1 row in set

104是h的ASCII值

2.输出b和B的ASCII值

mysql> SELECT ASCII(\'b\')AS Lower_Case, ASCII(\'B\') AS Upper_Case;
+————+————+
| Lower_Case | Upper_Case |
+————+————+
|         98 |         66 |
+————+————+
1 row in set

3.在where语句中使用ASCII函数

输出aut_name首字母的ASCII值小于70的数据

SELECT aut_name,ASCII(aut_name)as \"ASCII value of 1st character\"   
FROM author   
WHERE ASCII(aut_name)<70;

4.输出字段中不存在没有ASCII值的数据

SELECT * FROM table_name WHERE NOT column_to_check REGEXP \'[A-Za-z0-9.,-]\';

5.与SUBSTRING一起使用计算字符串第二个以后的ASCII值

mysql> select ASCII(SUBSTRING(\'data \',2,1));
+———————————-+
| ASCII(SUBSTRING(\'data \',2,1)) |
+———————————-+
|                               97 |
+———————————-+
1 row in set

ORD() 函数

ORD() 函数返回字符串第一个字符的ASCII 值。

语法： ORD(string)

举一些简单的例子：

mysql> SELECT ORD(\'i\');
+----------+
| ORD(\'i\') |
+----------+
|      105 |
+----------+
1 row in set

或者：

mysql> SELECT ORD(\'NowaMagic\');
+------------------+
| ORD(\'NowaMagic\') |
+------------------+
|               78 |
+------------------+
1 row in set

如果汉字又如何呢？

mysql> SELECT ORD(\'简明现代魔法\');
+---------------------+
| ORD(\'简明现代魔法\') |
+---------------------+
|            15183488 |
+---------------------+
1 row in set

mysql> SELECT ORD(\'简\');
+-----------+
| ORD(\'简\') |
+-----------+
|  15183488 |
+-----------+
1 row in set

为什么会有 8 位数那么长呢？原因是数据库使用的字符集问题，此处的数据库使用的是 UTF-8，16位表示一个符号。顺便贴一下SQL的执行语句：

mysql> SHOW CHARACTER SET;
+----------+-----------------------------+---------------------+--------+
| Charset  | De ion                 | Default collation   | Maxlen |
+----------+-----------------------------+---------------------+--------+
| big5     | Big5 Traditional Chinese    | big5_chinese_ci     |      2 |
| dec8     | DEC West European           | dec8_swedish_ci     |      1 |
| cp850    | DOS West European           | cp850_general_ci    |      1 |
| hp8      | HP West European            | hp8_english_ci      |      1 |
| koi8r    | KOI8-R Relcom Russian       | koi8r_general_ci    |      1 |
| latin1   | cp1252 West European        | latin1_swedish_ci   |      1 |
| latin2   | ISO 8859-2 Central European | latin2_general_ci   |      1 |
| swe7     | 7bit Swedish                | swe7_swedish_ci     |      1 |
| ascii    | US ASCII                    | ascii_general_ci    |      1 |
| ujis     | EUC-JP Japanese             | ujis_japanese_ci    |      3 |
| sjis     | Shift-JIS Japanese          | sjis_japanese_ci    |      2 |
| hebrew   | ISO 8859-8 Hebrew           | hebrew_general_ci   |      1 |
| tis620   | TIS620 Thai                 | tis620_thai_ci      |      1 |
| euckr    | EUC-KR Korean               | euckr_korean_ci     |      2 |
| koi8u    | KOI8-U Ukrainian            | koi8u_general_ci    |      1 |
| gb2312   | GB2312 Simplified Chinese   | gb2312_chinese_ci   |      2 |
| greek    | ISO 8859-7 Greek            | greek_general_ci    |      1 |
| cp1250   | Windows Central European    | cp1250_general_ci   |      1 |
| gbk      | GBK Simplified Chinese      | gbk_chinese_ci      |      2 |
| latin5   | ISO 8859-9 Turkish          | latin5_turkish_ci   |      1 |
| armscii8 | ARMSCII-8 Armenian          | armscii8_general_ci |      1 |
| utf8     | UTF-8 Unicode               | utf8_general_ci     |      3 |
| ucs2     | UCS-2 Unicode               | ucs2_general_ci     |      2 |
| cp866    | DOS Russian                 | cp866_general_ci    |      1 |
| keybcs2  | DOS Kamenicky Czech-Slovak  | keybcs2_general_ci  |      1 |
| macce    | Mac Central European        | macce_general_ci    |      1 |
| macroman | Mac West European           | macroman_general_ci |      1 |
| cp852    | DOS Central European        | cp852_general_ci    |      1 |
| latin7   | ISO 8859-13 Baltic          | latin7_general_ci   |      1 |
| utf8mb4  | UTF-8 Unicode               | utf8mb4_general_ci  |      4 |
| cp1251   | Windows Cyrillic            | cp1251_general_ci   |      1 |
| utf16    | UTF-16 Unicode              | utf16_general_ci    |      4 |
| cp1256   | Windows Arabic              | cp1256_general_ci   |      1 |
| cp1257   | Windows Baltic              | cp1257_general_ci   |      1 |
| utf32    | UTF-32 Unicode              | utf32_general_ci    |      4 |
| binary   | Binary pseudo charset       | binary              |      1 |
| geostd8  | GEOSTD8 Georgian            | geostd8_general_ci  |      1 |
| cp932    | SJIS for Windows Japanese   | cp932_japanese_ci   |      2 |
| eucjpms  | UJIS for Windows Japanese   | eucjpms_japanese_ci |      3 |
+----------+-----------------------------+---------------------+--------+
39 rows in set