Tracking Down Duplicates : COUNT « Aggregate Functions « SQL / MySQL

1. SQL / MySQL
2. Aggregate Functions
3. COUNT

Tracking Down Duplicates

        
mysql> CREATE TABLE authors (
    ->   authID int(11) NOT NULL auto_increment PRIMARY KEY ,
    ->   authName varchar(60),
    ->   ts timestamp
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql>
mysql>
mysql>
mysql>
mysql> INSERT INTO authors VALUES (1,'Tom','2004-12-02 18:36:51'),
    ->                              (2,'Jack','2004-12-02 18:36:51'),
    ->                              (3,'Jane','2004-12-02 18:36:51'),
    ->                              (4,'Amy','2004-12-02 18:36:51'),
    ->                              (5,'Bob','2004-12-02 18:36:51'),
    ->                              (6,'Race','2004-12-02 18:36:51'),
    ->                              (7,'Green','2004-12-02 18:36:51');
Query OK, 7 rows affected (0.00 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql>
mysql>
mysql> SELECT authName, COUNT(*) AS cnt
    -> FROM authors
    -> GROUP BY authName
    -> HAVING cnt>1;
Empty set (0.00 sec)

mysql>
mysql> drop table authors;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql>

   
    
    
    
    
    
    
    
  

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