在新的 MySQL 列中计算相同的字符串？
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)