April 2026
Beginner
493 pages
23h 2m
English
Content preview from SQL
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A.3 Relationships Among Entities
Since we’ve built a handful of tables and diagrams ourselves, it’s obvious to us that the product.product_cat_id column refers to the product_cat.id column. It’s also obvious to us that product.brand_id refers to brand.id. Picking self-explanatory and intuitive column names helps with that.
However, we can’t assume that everyone looking at the diagram can intuitively figure out such relationships, and don’t let the simplicity of our humble example make you think otherwise. Most users would need to have industry and/or process knowledge to understand many database schemas intuitively.
Therefore, it’s a good practice to draw table relationships in ERDs. While drawing relationships, it’s typical for us to include ...
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