SQL-通配符 


SQL-通配符


我们已经讨论过SQL LIKE运算符,该运算符用于使用通配符运算符将值与相似值进行比较。

SQL与LIKE运算符一起支持两个通配符运算符符,下表对此进行了详细说明。

Sr.No. Wildcard & Description
1

The percent sign (%)

Matches one or more characters.

Note − MS Access uses the asterisk (*) wildcard character instead of the percent sign (%) wildcard character.

2

The underscore (_)

Matches one character.

Note − MS Access uses a question mark (?) instead of the underscore (_) to match any one character.

百分号代表零个,一个或多个字符。下划线表示单个数字或字符。这些符号可以组合使用。

句法

‘%’和’_’运算符的基本语法如下。

SELECT * FROM table_name
WHERE column LIKE 'XXXX%'

or 

SELECT * FROM table_name
WHERE column LIKE '%XXXX%'

or

SELECT * FROM table_name
WHERE column LIKE 'XXXX_'

or

SELECT * FROM table_name
WHERE column LIKE '_XXXX'

or

SELECT * FROM table_name
WHERE column LIKE '_XXXX_'

您可以使用AND或OR运算符组合N个条件。在此,XXXX可以是任何数字或字符串值。

下表列出了许多示例,这些示例显示了WHERE部分,其中的不同LIKE子句带有’%’和’_’运算符。

Sr.No. Statement & Description
1

WHERE SALARY LIKE ‘200%’

Finds any values that start with 200.

2

WHERE SALARY LIKE ‘%200%’

Finds any values that have 200 in any position.

3

WHERE SALARY LIKE ‘_00%’

Finds any values that have 00 in the second and third positions.

4

WHERE SALARY LIKE ‘2_%_%’

Finds any values that start with 2 and are at least 3 characters in length.

5

WHERE SALARY LIKE ‘%2’

Finds any values that end with 2.

6

WHERE SALARY LIKE ‘_2%3’

Finds any values that have a 2 in the second position and end with a 3.

7

WHERE SALARY LIKE ‘2___3’

Finds any values in a five-digit number that start with 2 and end with 3.

让我们举一个真实的例子,考虑具有以下记录的CUSTOMERS表。

+----+----------+-----+-----------+----------+
| ID | NAME     | AGE | ADDRESS   | SALARY   |
+----+----------+-----+-----------+----------+
|  1 | Ramesh   |  32 | Ahmedabad |  2000.00 |
|  2 | Khilan   |  25 | Delhi     |  1500.00 |
|  3 | kaushik  |  23 | Kota      |  2000.00 |
|  4 | Chaitali |  25 | Mumbai    |  6500.00 |
|  5 | Hardik   |  27 | Bhopal    |  8500.00 |
|  6 | Komal    |  22 | MP        |  4500.00 |
|  7 | Muffy    |  24 | Indore    | 10000.00 |
+----+----------+-----+-----------+----------+

下面的代码块是一个示例,它将显示CUSTOMERS表中SALARY以200开头的所有记录。

SQL> SELECT * FROM CUSTOMERS
WHERE SALARY LIKE '200%';

这将产生以下结果。

+----+----------+-----+-----------+----------+
| ID | NAME     | AGE | ADDRESS   | SALARY   |
+----+----------+-----+-----------+----------+
|  1 | Ramesh   |  32 | Ahmedabad |  2000.00 |
|  3 | kaushik  |  23 | Kota      |  2000.00 |
+----+----------+-----+-----------+----------+
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