Convert ER model into a relational database schema expressed in SQL DDL, with appropriate constraints.

Use Create Table Command create table USER and PERSON:

Users and People

The following diagram shows the entities, attributes and relationships that provide the information about people on the pic.net site.

Comments on People:

we use a numeric ID as a primary key, since People and Users will be extensively referenced in the database

for every person in the database, we need to know their name

note the use of is-a in a circle to indicate that the Person entity has only a single sub-class (User); remember that you must implement this (very small) class hierarchy via the ER-style mapping

Comments on Users:

every user is required to provide password and an email address

the system records the date when they registered

users may provide additional data such as their birthday (date) and their gender ('male', 'female'); these fields can be NULL if users would rather not specify

all people have a name for the system to display them as; users may provide such a name for themselves; if no name is supplied, mypics.net will form a name from the family- and given-names

we assume that names are no longer than 50 chars (for the given-names and family-name components) and up to 100 chars for displayed names

a user's website (if supplied) is simply a URL text string

users may supply a portrait to be displayed when they are referenced on the website; this portrait is a photo of them in JPEG format