Question
Convert a ER model into a relational database schema expressed in SQL DDL, with appropriate constraints. Use Create Table Command Discussions and Comments The following
Convert a ER model into a relational database schema expressed in SQL DDL, with appropriate constraints.
Use Create Table Command
Discussions and Comments
The following diagram shows entities, attributes and relationships for the discussions and comments in the pics.net site.
Comments on Discussions:
discussions are essentially holders for collections of comments
each discussion has an identifying numeric ID and may have a title (up to 50 chars)
a discussion contains one or more comments and is created when the first comment is posted
a collection of comments on one photo needs no title; the discussion is associated with the photo being commented on
discussions under a group will have a title and will be associated the group
Comments on Comments:
comments are messages posted by users as part of a discussion
each comment has an identifying numeric ID
the system time-stamps each comment with the precise posting date and time
the content of a comment is an arbitrary text string
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