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如何在 MySQL 中判断中文字符？

2016-06-29 10:48 676 查看

如何在 MySQL 中判断中文字符？

http://blog.jobbole.com/94567/
一引子
在生产环境中，经常会有这样的场景：获得中文数据。那问题就来了，怎么才能匹配出中文字符呢？

本文提供两种方法。

二演示

2.1 环境

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2.2 创建测试表和插入测试数据

MySQL

mysql -S /tmp/mysql_5173.sock -uroot -proot

1	mysql -S /tmp/mysql_5173.sock -uroot -proot

创建测试表和插入测试数据。

MySQL

mysql> USE test;
Database changed

mysql> CREATE TABLE user
-> (name VARCHAR(20)
-> ) DEFAULT CHARSET = utf8 ENGINE = INNODB;
Query OK, 0 rows affected (0.10 sec)

mysql> SHOW TABLE STATUS LIKE 'user' G;
*************************** 1. row ***************************
Name: user
Engine: InnoDB
Version: 10
Row_format: Compact
Rows: 2
Avg_row_length: 8192
Data_length: 16384
Max_data_length: 0
Index_length: 0
Data_free: 0
Auto_increment: NULL
Create_time: 2015-01-16 18:01:36
Update_time: NULL
Check_time: NULL
Collation: utf8_general_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)

ERROR:
No query specified

mysql> INSERT INTO user VALUES('robin');
Query OK, 1 row affected (0.01 sec)

mysql> INSERT INTO user VALUES('温国兵');
Query OK, 1 row affected (0.00 sec)

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mysql>
USE test;

Database changed

mysql> CREATE
TABLE user
    ->
(name VARCHAR(20)

    ->  )
DEFAULT CHARSET
= utf8 ENGINE
= INNODB;
Query
OK, 0 rows
affected (0.10
sec)

mysql>
SHOW TABLE STATUS
LIKE 'user'
G;

*************************** 1.
row ***************************

Name: user

         Engine:
InnoDB
        Version:
10

     Row_format:
Compact

Rows: 2

Avg_row_length:
8192
    Data_length:
16384

Max_data_length: 0

Index_length: 0

      Data_free: 0
Auto_increment:
NULL

    Create_time: 2015-01-16
18:01:36
    Update_time:
NULL

     Check_time: NULL
      Collation:
utf8_general_ci

       Checksum:
NULL
Create_options:

        Comment:

1
row in
set (0.00
sec)

ERROR:

No query
specified

mysql> INSERT
INTO user
VALUES('robin');
Query
OK, 1 row
affected (0.01
sec)

mysql>
INSERT INTO
user VALUES('温国兵');

Query OK, 1
row affected
(0.00 sec)

三实现

3.1 方法一正则表达式

MySQL

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)

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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

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)

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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

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