如何检查MySQL中的值是否为整数？

我看到在MySQL中，有Cast()和Convert()函数可以从值创建整数，但是有什么方法可以检查值是否是整数？is_int()我正在寻找PHP中类似的东西。

我假设您要检查一个字符串值。一种不错的方法是REGEXP运算符，将字符串与正则表达式匹配。简单地做

select field from table where field REGEXP '^-?[0-9]+$';

这相当快。如果您的字段是数字，则只需测试

ceil(field) = field

代替。

将其与正则表达式匹配。

cf http://forums.mysql.com/read.php?60,1907,38488#msg-38488，如下所示：

Re：MySQL中的IsNumeric（）子句？
发表者：kevinclark（）
Date：2005年8月8日01:01 PM

我同意。这是我为MySQL 5创建的函数：

CREATE FUNCTION IsNumeric (sIn varchar(1024)) RETURNS tinyint
RETURN sIn REGEXP '^(-|\\+){0,1}([0-9]+\\.[0-9]*|[0-9]*\\.[0-9]+|[0-9]+)$';

这样可以在开头添加一个可选的正/负号，一个可选的小数点和其余数字。

假设我们有一个包含字母数字字段的列，其条目类似于

a41q
1458
xwe8
1475
asde
9582
.
.
.
.
.
qe84

并且您想要此数据库列中的最高数值（在这种情况下为9582），那么此查询将为您提供帮助

SELECT Max(column_name) from table_name where column_name REGEXP '^[0-9]+$'

这是假设数据类型为varchar的简单解决方案

select * from calender where year > 0

如果年份为数字，则返回true，否则返回false

这也适用：

CAST( coulmn_value AS UNSIGNED ) // will return 0 if not numeric string.

例如

SELECT CAST('a123' AS UNSIGNED) // returns 0
SELECT CAST('123' AS UNSIGNED) // returns 123 i.e. > 0

要检查Mysql中的值是否为Int，我们可以使用以下查询。该查询将为行提供Int值

SELECT col1 FROM table WHERE concat('',col * 1) = col;

我能想到的最好的一个变量是int是与MySQL函数CAST()和的组合LENGTH()。
此方法适用于字符串，整数，双精度/浮点型数据类型。

SELECT (LENGTH(CAST(<data> AS UNSIGNED))) = (LENGTH(<data>)) AS is_int

参见演示http://sqlfiddle.com/#!9/ff40cd/44

如果该列具有单个字符值，它将失败。如果列的值为'A'，则Cast（'A'为UNSIGNED）的值将为0，而LENGTH（0）将为1。因此LENGTH（Cast（'A'为UNSIGNED））= LENGTH（0）的值将为1 = 1 => 1

真正的Waqas Malik完全怀疑这件事。补丁是。

SELECT <data>, (LENGTH(CAST(<data> AS UNSIGNED))) = CASE WHEN CAST(<data> AS UNSIGNED) = 0 THEN CAST(<data> AS UNSIGNED) ELSE (LENGTH(<data>)) END AS is_int;

结果

**Query #1**

    SELECT 1, (LENGTH(CAST(1 AS UNSIGNED))) = CASE WHEN CAST(1 AS UNSIGNED) = 0 THEN CAST(1 AS UNSIGNED) ELSE (LENGTH(1)) END AS is_int;

| 1   | is_int |
| --- | ------ |
| 1   | 1      |

---
**Query #2**

    SELECT 1.1, (LENGTH(CAST(1 AS UNSIGNED))) = CASE WHEN CAST(1.1 AS UNSIGNED) = 0 THEN CAST(1.1 AS UNSIGNED) ELSE (LENGTH(1.1)) END AS is_int;

| 1.1 | is_int |
| --- | ------ |
| 1.1 | 0      |

---
**Query #3**

    SELECT "1", (LENGTH(CAST("1" AS UNSIGNED))) = CASE WHEN CAST("1" AS UNSIGNED) = 0 THEN CAST("1" AS UNSIGNED) ELSE (LENGTH("1")) END AS is_int;

| 1   | is_int |
| --- | ------ |
| 1   | 1      |

---
**Query #4**

    SELECT "1.1", (LENGTH(CAST("1.1" AS UNSIGNED))) = CASE WHEN CAST("1.1" AS UNSIGNED) = 0 THEN CAST("1.1" AS UNSIGNED) ELSE (LENGTH("1.1")) END AS is_int;

| 1.1 | is_int |
| --- | ------ |
| 1.1 | 0      |

---
**Query #5**

    SELECT "1a", (LENGTH(CAST("1.1" AS UNSIGNED))) = CASE WHEN CAST("1a" AS UNSIGNED) = 0 THEN CAST("1a" AS UNSIGNED) ELSE (LENGTH("1a")) END AS is_int;

| 1a  | is_int |
| --- | ------ |
| 1a  | 0      |

---
**Query #6**

    SELECT "1.1a", (LENGTH(CAST("1.1a" AS UNSIGNED))) = CASE WHEN CAST("1.1a" AS UNSIGNED) = 0 THEN CAST("1.1a" AS UNSIGNED) ELSE (LENGTH("1.1a")) END AS is_int;

| 1.1a | is_int |
| ---- | ------ |
| 1.1a | 0      |

---
**Query #7**

    SELECT "a1", (LENGTH(CAST("1.1a" AS UNSIGNED))) = CASE WHEN CAST("a1" AS UNSIGNED) = 0 THEN CAST("a1" AS UNSIGNED) ELSE (LENGTH("a1")) END AS is_int;

| a1  | is_int |
| --- | ------ |
| a1  | 0      |

---
**Query #8**

    SELECT "a1.1", (LENGTH(CAST("a1.1" AS UNSIGNED))) = CASE WHEN CAST("a1.1" AS UNSIGNED) = 0 THEN CAST("a1.1" AS UNSIGNED) ELSE (LENGTH("a1.1")) END AS is_int;

| a1.1 | is_int |
| ---- | ------ |
| a1.1 | 0      |

---
**Query #9**

    SELECT "a", (LENGTH(CAST("a" AS UNSIGNED))) = CASE WHEN CAST("a" AS UNSIGNED) = 0 THEN CAST("a" AS UNSIGNED) ELSE (LENGTH("a")) END AS is_int;

| a   | is_int |
| --- | ------ |
| a   | 0      |

观看演示

关于什么：

WHERE table.field = "0" or CAST(table.field as SIGNED) != 0

测试数字和颜色：

WHERE table.field != "0" and CAST(table.field as SIGNED) = 0

我已经尝试使用上面列出的正则表达式，但是它们不适用于以下情况：

SELECT '12 INCHES' REGEXP '^(-|\\+){0,1}([0-9]+\\.[0-9]*|[0-9]*\\.[0-9]+|[0-9]+)$' FROM ...

上面的代码将返回1（TRUE），表示针对字符串'12 INCHES'对上面的正则表达式进行测试TRUE。根据上面使用的正则表达式，它看起来像一个数字。在这种情况下，由于12在字符串的开头，因此正则表达式将其解释为数字。

以下内容将返回正确的值（即0），因为字符串以字符而不是数字开头

SELECT 'TOP 10' REGEXP '^(-|\\+){0,1}([0-9]+\\.[0-9]*|[0-9]*\\.[0-9]+|[0-9]+)$' FROM ...

上面的将返回0（FALSE），因为字符串的开头是文本而不是数字。

但是，如果要处理包含数字和以数字开头的字母的混合字符串，则不会获得所需的结果。实际上，REGEXP会将字符串解释为有效数字。

这对于以数字开头或不以数字开头的VARCHAR都适用。

WHERE concat('',fieldname * 1) != fieldname 

当您使用较大的NNNNE +号时，可能会有限制

对我而言，唯一有效的方法是：

CREATE FUNCTION IsNumeric (SIN VARCHAR(1024)) RETURNS TINYINT
RETURN SIN REGEXP '^(-|\\+){0,1}([0-9]+\\.[0-9]*|[0-9]*\\.[0-9]+|[0-9]+)$';

从kevinclark对我的情况下，所有其他返回无用的东西234jk456或12 inches