Are you making this #1 SQL Error?
Today I talk about SQL cardinality, which defines the relationships between two SQL tables in a database. We explore how this can lead to repeat rows which can inflate your data later on, when you plug the data into a dashboard or do analysis.
Note, all patient data contained within this video is fake, and generated by Synthea.
Error @6:11 a many to many will cause extra rows as well. Many to many isn't used very often though.
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Point of clarification: at
Covid Vaccine: 12:07, I meant to say "How many patients with Covid Vaccines did we have?"
A good guide on ERDs and crow's foot notation:
https://www.smartdraw.com/entity-rela...
Check out my previous video here if you would like to learn joins:
• SQL Joins Made VERY SIMPLE!
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