如何从mysql中只选择数值型数据？
如何从mysql中只选择数值型数据？
提问于 2010-05-03 15:41:21
mysql有没有像is_num()这样的函数，可以让我判断数据是不是数字？
回答 6
Stack Overflow用户
发布于 2010-05-03 16:06:49
您可能希望创建一个用户定义的函数，该函数将该值与正则表达式进行匹配：
CREATE FUNCTION IsNumeric (sIn varchar(1024)) RETURNS tinyint
RETURN sIn REGEXP '^(-|\\+){0,1}([0-9]+\\.[0-9]*|[0-9]*\\.[0-9]+|[0-9]+)$'; 来源：MySQL Forums :: Microsoft SQL Server :: IsNumeric() clause in MySQL?
真实测试：
mysql> SELECT ISNUMERIC('1');
+----------------+
| ISNUMERIC('1') |
+----------------+
| 1 |
+----------------+
1 row in set (0.01 sec)
mysql> SELECT ISNUMERIC(25);
+---------------+
| ISNUMERIC(25) |
+---------------+
| 1 |
+---------------+
1 row in set (0.00 sec)
mysql> SELECT ISNUMERIC('-100');
+-----------------+
| ISNUMERIC(-100) |
+-----------------+
| 1 |
+-----------------+
1 row in set (0.03 sec)
mysql> SELECT ISNUMERIC('1.5');
+------------------+
| ISNUMERIC('1.5') |
+------------------+
| 1 |
+------------------+
1 row in set (0.00 sec)
mysql> SELECT ISNUMERIC('-1.5');
+-------------------+
| ISNUMERIC('-1.5') |
+-------------------+
| 1 |
+-------------------+
1 row in set (0.02 sec)Falsy测试：
mysql> SELECT ISNUMERIC('a');
+----------------+
| ISNUMERIC('a') |
+----------------+
| 0 |
+----------------+
1 row in set (0.02 sec)
mysql> SELECT ISNUMERIC('a1');
+-----------------+
| ISNUMERIC('a1') |
+-----------------+
| 0 |
+-----------------+
1 row in set (0.00 sec)
mysql> SELECT ISNUMERIC('10a');
+------------------+
| ISNUMERIC('10a') |
+------------------+
| 0 |
+------------------+
1 row in set (0.00 sec)
mysql> SELECT ISNUMERIC('0.a');
+------------------+
| ISNUMERIC('0.a') |
+------------------+
| 0 |
+------------------+
1 row in set (0.00 sec)
mysql> SELECT ISNUMERIC('a.0');
+------------------+
| ISNUMERIC('a.0') |
+------------------+
| 0 |
+------------------+
1 row in set (0.00 sec)Stack Overflow用户
发布于 2010-05-16 02:15:22
在我的例子中，我只需要检查数据是否是>= 0而不是char，也许这对您也很有用：
mysql> select '1' REGEXP '^[0-9]+$' as result;
+--------+
| result |
+--------+
| 1 |
+--------+
1 row in set (0.16 sec)
mysql> select '1a' REGEXP '^[0-9]+$' as result;
+--------+
| result |
+--------+
| 0 |
+--------+Stack Overflow用户
发布于 2011-01-30 07:46:06
如果只想从字符串中选择数字字符，请尝试使用以下命令：
CREATE FUNCTION IsNumeric (val varchar(255)) RETURNS tinyint
RETURN val REGEXP '^(-|\\+){0,1}([0-9]+\\.[0-9]*|[0-9]*\\.[0-9]+|[0-9]+)$';
CREATE FUNCTION NumericOnly (val VARCHAR(255))
RETURNS VARCHAR(255)
BEGIN
DECLARE idx INT DEFAULT 0;
IF ISNULL(val) THEN RETURN NULL; END IF;
IF LENGTH(val) = 0 THEN RETURN ""; END IF;
SET idx = LENGTH(val);
WHILE idx > 0 DO
IF IsNumeric(SUBSTRING(val,idx,1)) = 0 THEN
SET val = REPLACE(val,SUBSTRING(val,idx,1),"");
SET idx = LENGTH(val)+1;
END IF;
SET idx = idx - 1;
END WHILE;
RETURN val;
END;通过调用NumericOnly函数使用它，如下所示：
select NumericOnly('1&2') as result;返回："12“
select NumericOnly('abc987') as result;返回："987“
(顺便说一句，我写了一个post about this here)
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/2756736
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