The first column seems to be a hidden column called 'id' for the primary key in the WFA database. The \N tells mysql it's a null field, so mysql creates its own value. You could put your own key in there instead of \N if you wanted to.
View the Data Source script for the vc Scheme under "Data Source Types" --> "VMware vCenter" as an example. This one script updates several dictionary objects at one time. Note some of the tab delimited CSV files it creates have \N as the first column, while others use a unique identifier like the Host object ($hostFile) starts out with a $hostId that it gets from the (object returned from Get-VMHost)'s Id.GetHashCode() call. If you look at the Host dictionary object, there is no HostID listed. The dictionary object starts with the 2nd column in the CSV, the Name parameter.
Add-Content $hostFile ([byte[]][char[]] "$hostId`t$name`t$ip`t$os_version`t$virtualCenterIp`t$cluster`t$datacenterName`n") -Encoding Byte
I looked at the table structure in mysql, and confirmed the first column is the primary key for the table, and it doesn't map back to anything listed in the dictionary object definition.
mysql> use vc;
Database changed
mysql> show tables;
+-----------------+
| Tables_in_vc |
+-----------------+
| data_store |
| host |
| lun |
| nas_share |
| virtual_disk |
| virtual_machine |
+-----------------+
6 rows in set (0.00 sec)
mysql> show columns from host;
+-------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(255) | NO | MUL | NULL | |
| ip | varchar(255) | YES | | NULL | |
| os_version | varchar(255) | YES | | NULL | |
| virtual_center_ip | varchar(255) | NO | | NULL | |
| cluster_name | varchar(255) | YES | | NULL | |
| data_center_name | varchar(255) | YES | | NULL | |
+-------------------+--------------+------+-----+---------+----------------+
7 rows in set (0.03 sec)
mysql>

Hope this helps,
Dave