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AI, Data Science, & Programming for Small Business Applications & Large Enterprises › Forums › SQL › Help understanding ER diagram
https://www.coursera.org/learn/sql-for-data-science
An explanation of why few tables are kept black as well how to make sense of primary key and infinity symbol appreciated.
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It appears that some entities are blacked out because they really do not matter for the question being asked.
The primary key symbol identifies the column(s) that make up the primary key.
The infinity symbol identifies one-to-many relationships.