三 实现
　　3.1 方法一 正则表达式
mysql> SELECT * FROM user G;
*************************** 1. row ***************************
name: robin
*************************** 2. row ***************************
name: 温国兵
2 rows in set (0.00 sec)
mysql> SELECT name，
->     CASE name REGEXP "[u0391-uFFE5]"
->         WHEN 1 THEN "不是中文字符"
->         ELSE "是中文字符"
->     END AS "判断是否是中文字符"
-> FROM user;
+
-----------+-----------------------------+
| name      | 判断是否是中文字符 |
+
-----------+-----------------------------+
| robin     | 不是中文字符          |
| 温国兵 | 是中文字符             |
+
-----------+-----------------------------+
2 rows in set (0.00 sec)
mysql> SELECT name FROM user WHERE NOT (name REGEXP "[u0391-uFFE5]");
+
-----------+
| name      |
+
-----------+
| 温国兵 |
+
-----------+
1 row in set (0.00 sec)
　　3.2 方法二 length() 和 char_length()
mysql> SELECT name， length(name)， char_length(name) FROM user;
+
-----------+--------------+-------------------+
| name      | length(name) | char_length(name) |
+
-----------+--------------+-------------------+
| robin     |            5 |                 5 |
| 温国兵 |           20 |                 9 |
+
-----------+--------------+-------------------+
2 rows in set (0.00 sec)
mysql> SELECT name FROM user WHERE length(name)  char_length(name);
+
-----------+
| name      |
+
-----------+
| 温国兵 |
+
-----------+
1 row in set (0.00 sec)
　　四 总结
　　方法一中，[u0391-uFFE5] 匹配中文以外的字符。
　　方法二中，当字符集为UTF-8，并且字符为中文时，length() 和 char_length() 两个方法返回的结果不相同。
　　参考官方文档：
　　LENGTH()
　　Return the length of a string in bytes
　　Returns the length of the string str， measured in bytes. A multibyte character counts as multiple bytes. This means that for a string containing five 2-byte characters， LENGTH() returns 10， whereas CHAR_LENGTH() returns 5.
　　CHAR_LENGTH()
　　Return number of characters in argument
　　Returns the length of the string str， measured in characters. A multibyte character counts as a single character. This means that for a string containing five 2-byte characters， LENGTH() returns 10， whereas CHAR_LENGTH() returns 5.
　　五 Ref
　　12.5 String Functions