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I've been handed the ER diagram for a quite complex database. Complex to me at least, 849 tables. One of the architects says to understand the code, you need to understand the database and relationships.

Now I am basically a Java programmer hence not too familiar with this

How do I start? Should I start from something basic like USER or ORDER and see which relationships they have with other tables around them?

Any tips or tutorials would help a lot

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An ER Diagram is out there to visualize a design, which was made to accomplish a certain job. Understand what the job is first, then ask questions to the diagram.

"How is an order stored?", "How do I retrieve user information", "How can I tell which user ordered a certain product between these intervals and with these options?". Such questions might help you understand the design. If there is a requirements analysis documentation, it will help you a lot with coming up with these questions. You can explore how certain requirements are handled.

I suspect that a database with 849 tables is highly normalized so most of those tables might be lookup tables which does not have much effect on the relationships of the entities. Try to focus on the parent tables holding keys to those lookup tables.

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An Entity Relationship Diagram (ERD) is a visual representation of different entities within a system and how they relate to each other.First of all you have to know basic notation and use of that notation.and understand basic information like entity,Relation ship and attribute and than you can easily understand diagram.

Please refer below for more information:

https://www.guru99.com/er-diagram-tutorial-dbms.html

https://creately.com/blog/diagrams/er-diagrams-tutorial/

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