mysql> use tutorials;
Database changed
mysql> create table person(id int, name varchar(32));
Query OK, 0 rows affected (0.22 sec)
mysql> insert into person values(1,'Thomas');
Query OK, 1 row affected (0.09 sec)
mysql> insert into person values(2,'Thomas');
Query OK, 1 row affected (0.04 sec)
mysql> insert into person values(3,'Ralf');
Query OK, 1 row affected (0.04 sec)
mysql> insert into person values(3,'Ralf');
Query OK, 1 row affected (0.05 sec)
mysql> insert into person values(4,'Stephan');
Query OK, 1 row affected (0.06 sec)
mysql> select * from person;
+------+---------+
| id | name |
+------+---------+
| 1 | Thomas |
| 2 | Thomas |
| 3 | Ralf |
| 3 | Ralf |
| 4 | Stephan |
+------+---------+
5 rows in set (0.05 sec)
//Alle Sätze die im Sinne eines "gleichen" Namens doppelt sind:
mysql> select name, count(name) cnt from person group by name having cnt > 1 ;
+--------+-----+
| name | cnt |
+--------+-----+
| Ralf | 2 |
| Thomas | 2 |
+--------+-----+
2 rows in set (0.06 sec)
//Alle sätze die im Sinne aller Attribute doppelt sind.
mysql> select id,name, count(name) cnt from person group by id,name having cnt > 1 ;
+------+------+-----+
| id | name | cnt |
+------+------+-----+
| 3 | Ralf | 2 |
+------+------+-----+
1 row in set (0.00 sec)
