Question

我在MySQL中看到有Cast()和Convert()函数从值创建整数，但有没有办法检查一个值是否为整数？像PHP中的is_int()这样的东西就是我要找的东西。

Answer 1

我假设您要检查字符串值。一个很好的方法是REGEXP运算符，将字符串与正则表达式匹配。只需做

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

这是相当快的。如果您的字段是数字，只需测试

ceil(field) = field

代替。

Answer 2

将其与正则表达式匹配。

c.f。 http://forums.mysql.com/read.php?60,1907,38488#msg-38488引用如下：

Re：MySQL中的IsNumeric（）子句？
发布者：kevinclark（）
日期：2005年8月8日下午01:01


我同意。这是我为MySQL 5创建的一个函数：

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

这允许在开头有一个可选的加号/减号，一个可选的小数点和其余的数字。

Answer 3

假设我们的字段包含字母数字字段，其中包含

等条目

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

并且您希望此db列中的最高数值（在本例中为9582）然后此查询将帮助您

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

Answer 4

这是一个简单的解决方案假设数据类型是varchar

select * from calender where year > 0

如果年份为数字，则返回true，否则为false

Answer 5

这也有效：

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

Answer 6

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

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

Answer 7

怎么样：

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

测试数字和证据：

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

Answer 8

我已尝试使用上面列出的正则表达式，但它们不适用于以下内容：

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

以上将返回1（TRUE），这意味着对上面的正则表达式测试字符串'12 INCHES'，返回TRUE。它看起来像是基于上面使用的正则表达式的数字。在这种情况下，因为12位于字符串的开头，所以正则表达式将其解释为数字。

以下将返回正确的值（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 ...

以上内容将返回0（FALSE），因为字符串的开头是文字而不是数字。

但是，如果您要处理的数字和字母混合的字符串以数字开头，则无法获得所需的结果。 REGEXP会将字符串解释为有效数字，而实际上并非如此。

Answer 9

我能想到的最好的变量是int是与MySQL的函数CAST()和LENGTH()的组合。
此方法适用于字符串，整数，双精度/浮点数据类型。

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

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

如果列具有单个字符值，则
将失败。如果列有值'A'然后Cast（'A'作为UNSIGNED）将评估为0和 LENGTH（0）将为1. so LENGTH（Cast（'A'为UNSIGNED））= LENGTH（0）将评估为1 = 1 =＆gt; 1

True Waqas Malik完全模仿测试那个案子。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;

<强>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      |

请参阅demo

Answer 10

这适用于VARCHAR，它以数字开头或不是。

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

当你到达更大的NNNNE + - 数字

时，

可能会受到限制

Answer 11

对我来说唯一有用的是：

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

在234jk456或12 inches

的情况下，来自kevinclark的所有其他返回无用的内容

如何检查MySQL中的值是否为整数？

11 个答案: