Question

mysql是否有像is_num（）这样的函数可以让我确定数据是否为数字？

Answer 1

您可能想要创建一个用户定义的函数，该函数将值与正则表达式匹配：

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?

Truthy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 Tests：

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)

Answer 2

在我的情况下，我只需要检查数据是否是＆gt; = 0而不是char，也许这对你也很有用：

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 | 
+--------+

Answer 3

如果您只想从字符串中选择数字字符，请尝试使用：

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函数来使用它：

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post about this here）

Answer 4

只需使用DECIMAL或SIGNED / UNSIGNED将数据显式转换为数字，然后使用STRCMP与原始数据值进行比较。如果STRCMP返回0（相等），那么您知道您有一个数字。否则，它不是。

以下是一个示例，假设数据中的数字没有小数位，因此我们可以将其转换为DECIMAL。

此查询选择is_it_a_number字段中包含数字数据的所有行。

SELECT * FROM my_table WHERE
    STRCMP(CAST(my_table.is_it_a_number AS DECIMAL(10,0)), my_table.is_it_a_number) = 0;

Answer 5

从SQL到MYSQL的IsNumeric的简单语法是

SQL：

SELECT isNumeric(col_name) FROM Table where isNumeric(col_name) <> 0

Mysql的

select concat('',col_name * 1) from table where concat('',col_name * 1) <> 0;

Answer 6

快了一千倍。

DROP FUNCTION IF EXISTS NumericOnly;
DELIMITER $$
CREATE FUNCTION NumericOnly(val VARCHAR(25)) RETURNS VARCHAR(25)
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 (SUBSTRING(val,idx,1) in ('0','1','2','3','4','5','6','7','8','9')) = 0 THEN
   SET val = CONCAT(SUBSTRING(val, 1, idx-1), SUBSTRING(val FROM idx + 1));
  END IF;
  SET idx = idx - 1;
  END WHILE;
  RETURN val;
END;
$$
DELIMITER ;

如何只从mysql中选择数字数据？

6 个答案: