This article outlines the database structure for the MMv4 em_link database table.

• id
  Primary key of the em_link table.
  int(10) | unsigned | auto increment | primary key| indexed
  
• history_id
  System ID of the email history entry for the email associated with this link.
  int(10) | unsigned | indexed
• url
  The URL for this link.
  varchar(255) | indexed
• clicks
  The amount of times the link was clicked by the recipient.
  int(10) | unsigned | indexed
• edit_date
  The date this link was last modified.
  int(10) | unsigned | indexed