计算新 MySQL 列中的相同字符串?
mysqlmysqli database
使用 COUNT() 执行此操作。让我们首先创建一个表 −
mysql> create table DemoTable ( StudentFirstName varchar(20) ); Query OK, 0 rows affected (0.53 sec)
使用 insert 命令在表中插入记录 −
mysql> insert into DemoTable values('Larry');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable values('John');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable values('Larry');
Query OK, 1 row affected (0.10 sec)
mysql> insert into DemoTable values('David');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values('Bob');
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable values('Larry');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable values('David');
Query OK, 1 row affected (0.24 sec)
mysql> insert into DemoTable values('Larry');
Query OK, 1 row affected (0.14 sec)
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)
