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在新的 MySQL 列中计算相同的字符串？

2023-06-20 10:11:03 512

COUNT()为此使用。让我们首先创建一个表-

mysql> create table DemoTable
   (
   StudentFirstName varchar(20)
   );

使用插入命令在表中插入记录-

mysql> insert into DemoTable values('Larry');
mysql> insert into DemoTable values('John');
mysql> insert into DemoTable values('Larry');
mysql> insert into DemoTable values('David');
mysql> insert into DemoTable values('Bob');
mysql> insert into DemoTable values('Larry');
mysql> insert into DemoTable values('David');
mysql> insert into DemoTable values('Larry');

使用select语句显示表中的所有记录-

mysql> select * from DemoTable;

这将产生以下输出-

+------------------+
| StudentFirstName |
+------------------+
| Larry            |
| John             |
| Larry            |
| David            |
| Bob              |
| Larry            |
| David            |
| Larry            |
+------------------+
8 rows in set (0.00 sec)

以下是在MySQL中计算相同字符串的查询-

mysql> select StudentFirstName,concat(count(StudentFirstName),' times') from DemoTable
group by StudentFirstName;

这将产生以下输出-

+------------------+------------------------------------------+
| StudentFirstName | concat(count(StudentFirstName),' times') |
+------------------+------------------------------------------+
| Larry            | 4 times                                  |
| John             | 1 times                                  |
| David            | 2 times                                  |
| Bob              | 1 times                                  |
+------------------+------------------------------------------+
4 rows in set (0.00 sec)

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在新的 MySQL 列中计算相同的字符串？

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