Question

I have this table in a mysql database:

mysql> show columns from wifi_network_config_auth_algorithm;
+------------------------+-------------+------+-----+---------+-------+
| Field                  | Type        | Null | Key | Default | Extra |
+------------------------+-------------+------+-----+---------+-------+
| wifi_network_config_id | int(11)     | NO   | PRI | NULL    |       | 
| auth_algorithm         | varchar(50) | NO   | PRI | NULL    |       | 
+------------------------+-------------+------+-----+---------+-------+

The table was created using liquibase. Table creation itself does not define primary keys. Following table creation, the following liquibase command is used to set the combination of 2 columns as the primary key:

<addPrimaryKey tableName="wifi_network_config_auth_algorithm"
        columnNames="wifi_network_config_id,auth_algorithm"
        constraintName="pk_wifi_network_config_auth_algorithm"/>

Now, when you execute this to load data into this table:

LOCK TABLES `wifi_network_config_auth_algorithm` WRITE;
INSERT INTO `wifi_network_config_auth_algorithm` VALUES
(1, 'OPEN'),
(1, 'SHARED'),
(2, 'SHARED'),
(2, 'LEAP');
UNLOCK TABLES;

You get:

ERROR 1062 (23000): Duplicate entry '1' for key 2

Since the combination of both columns is the primary key, so the combination of the data in the two columns should be unique – which is true for the data shown above. Why is mysql complaining?

Also, it’s complaining that the value ‘1’ is being assigned to key 2, which does not make sense. I changed the INSERT to:

INSERT INTO `wifi_network_config_auth_algorithm` (`wifi_network_config_id`, `auth_algorithm`)

but it did not make any difference – same complaint from mysql.

Thanks,
Hari

Answer 1

Figured out the issue with @kbenson’s help. The answer is in the comments for the original question.