为此，请使用 MySQL 中的 CHAR_LENGTH() 函数。让我们首先创建一个表 -
mysql> create table DemoTable
(
Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
Subject longtext
);
Query OK, 0 rows affected (1.17 sec)
登录后复制
现在您可以使用插入命令在表中插入一些记录 -
mysql> insert into DemoTable(Subject) values('MySQL,MongoDB');
Query OK, 1 row affected (0.20 sec)
mysql> insert into DemoTable(Subject) values('MySQL,MongoDB');
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable(Subject) values('MongoDB');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable(Subject) values('MySQL');
Query OK, 1 row affected (0.15 sec)
Display all records from the table using select statement :
mysql> select *from DemoTable;
登录后复制
输出
+----+---------------+
| Id | Subject |
+----+---------------+
| 1 | MySQL,MongoDB |
| 2 | MySQL,MongoDB |
| 3 | MongoDB |
| 4 | MySQL |
+----+---------------+
4 rows in set (0.00 sec)
登录后复制
下面是通过对列中特定 id 的 MySQL 查询来查找字符串计数的查询。我们在这里检查 id 1 -
mysql> select Id,char_length(Subject) - char_length(REPLACE((Subject), ',', ''))+1
AS FreqSubject from DemoTable WHERE char_length(Subject) > 0 AND Id = 1;
登录后复制
输出
+----+-------------+
| Id | FreqSubject |
+----+-------------+
| 1 | 2 |
+----+-------------+
1 row in set (0.02 sec)
登录后复制
以上就是如何使用 MySQL 查询查找列中特定 id 的字符串计数？的详细内容，更多请关注每日运维网(www.mryunwei.com)其它相关文章！
