These are some considerations to help you a little bit.

1. They hold a lot of information about the module, module table and join tables on the relationship table.
2. The crm creates a unique id for the table id. No matter what table you are working with the primary id field must be named id and cannot be auto increment. If I’m not wrong the sugarbean will be responsible to generate this value wich looks like a hash: d6ee4529-56f0-3bc8-19b8-47cdbe4f2305
3. The user table works as exception from the previous statement. The primary key field is named id, but the key is composed by username followed by a dash and id. Ex. chris_id.
4. The user table also works as a group table. It has on the end a is_group flag.
5. Calendar is saved on the iCalendar format
   1. Example: BEGIN:VCALENDAR
      VERSION:2.0
      PRODID:-//SugarCRM//SugarCRM Calendar//EN
      BEGIN:VFREEBUSY
      ORGANIZER;CN= Administrator:
      DTSTART:20080303T212800Z
      DTEND:20080503T212800Z
      DTSTAMP:20080304T212800Z
      END:VFREEBUSY
      END:VCALENDAR
6. Module tables should be named as module name followed by submodule or action. Everything in lower case.
   1. Example: project; project_task; project_task_audit;
7. email_addr_bean_rel holds a bean_id that is the id of the table and a bean_module that is the table where it came from
8. Just like vTiger it have custom fields
9. No matter what module you are going to associate with, if there’s a user assigned to, the field will be name assigned_user_id. The exception is when the module table works with more than one module, so it will have to hold a bean (module, table) and a bean_id (the module, table, id). The same is true for holding the information for a user that modifies the record. In this case the field will be named modified_user_id.
10. In some tables date_modified will be the same as date_created