📅 最后修改于: 2020-11-26 06:23:02 🧑 作者: Mango
PostgreSQL LIKE运算符用于使用通配符将文本值与模式匹配。如果搜索表达式可以与模式表达式匹配，则LIKE运算符将返回true，即1 。
有两个通配符与LIKE运算符一起使用-
百分号代表零个，一个或多个数字或字符。下划线表示单个数字或字符。这些符号可以组合使用。
如果这两个符号中的任何一个都不与LIKE子句一起使用，则LIKE的行为类似于equals运算符。
％和_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。 XXXX可以是任何数字或字符串值。
这是一些示例，显示WHERE部分具有不同的LIKE子句，其中包含’％’和’_’运算符-
| S. No. | Statement & Description |
|---|---|
| 1 |
WHERE SALARY::text LIKE ‘200%’ Finds any values that start with 200 |
| 2 |
WHERE SALARY::text LIKE ‘%200%’ Finds any values that have 200 in any position |
| 3 |
WHERE SALARY::text LIKE ‘_00%’ Finds any values that have 00 in the second and third positions |
| 4 |
WHERE SALARY::text LIKE ‘2_%_%’ Finds any values that start with 2 and are at least 3 characters in length |
| 5 |
WHERE SALARY::text LIKE ‘%2’ Finds any values that end with 2 |
| 6 |
WHERE SALARY::text LIKE ‘_2%3’ Finds any values that have 2 in the second position and end with a 3 |
| 7 |
WHERE SALARY::text LIKE ‘2___3’ Finds any values in a five-digit number that start with 2 and end with 3 |
Postgres LIKE仅是String比较。因此，我们需要像上面的示例一样将整数列显式转换为字符串。
让我们以一个真实的例子为例，考虑表COMPANY ，其记录如下：
# select * from COMPANY;
id | name | age | address | salary
----+-------+-----+-----------+--------
1 | Paul | 32 | California| 20000
2 | Allen | 25 | Texas | 15000
3 | Teddy | 23 | Norway | 20000
4 | Mark | 25 | Rich-Mond | 65000
5 | David | 27 | Texas | 85000
6 | Kim | 22 | South-Hall| 45000
7 | James | 24 | Houston | 10000
(7 rows)
以下是一个示例，它将显示COMPANY表中AGE以2开头的所有记录-
testdb=# SELECT * FROM COMPANY WHERE AGE::text LIKE '2%';
这将产生以下结果-
id | name | age | address | salary
----+-------+-----+-------------+--------
2 | Allen | 25 | Texas | 15000
3 | Teddy | 23 | Norway | 20000
4 | Mark | 25 | Rich-Mond | 65000
5 | David | 27 | Texas | 85000
6 | Kim | 22 | South-Hall | 45000
7 | James | 24 | Houston | 10000
8 | Paul | 24 | Houston | 20000
(7 rows)
以下是一个示例，它将显示COMPANY表中的所有记录，其中ADDRESS在文本内将带有连字符(-)-
testdb=# SELECT * FROM COMPANY WHERE ADDRESS LIKE '%-%';
这将产生以下结果-
id | name | age | address | salary
----+------+-----+-------------------------------------------+--------
4 | Mark | 25 | Rich-Mond | 65000
6 | Kim | 22 | South-Hall | 45000
(2 rows)