Entity Relationship Diagram

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SQL - Cannot Add Foreign Key Constraint

Can anyone tell me why there are errors such as : Cannot Add Foreign Key Constraint And am i on the right track ? DROP DATABASE technology_university_hospital; CREATE DATABASE ...
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1answer
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How to define User/Permission relationship as M:M?

The Resource relates to Action as M:M via Permission join table/separate entity. User can have many permissions. The same permission may be assigned to multiple users. How to define User-Permission ...
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Relationship issue

I'm working on a ERD with mysql workbench, and i have a little question. I have a Database with this tables: company_address country state city I want to store the address of the company with all ...
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573 views

Which is the redundant relationship in this ER Diagram and why?

Which is the redundant relationship in this ER Diagram and why? A few of my friends and I have been trying to figure it out but keep going in circles. where the attributes of each entity are as ...
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The nature of the relationship between two tables in MySQL

Good day. I'm designing a database for a research project where we're predicting whether or not young female athletes will rupture their ACL(s) based on the nature of a test jump recorded with a ...
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help with this scenario ERD design

Can someone please show me how to construct this ER diagram with the following scenario, i'm confused with the 'or' part of it. Scenario An artist has a name, and must be either a group or a solo ...
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Entity relationship modelling, comment on my ERD

Note: Due to low reputation I can't post images so i have added the links accordingly. I have this assignment I'm working and I am stuck in a recursive relationship, following is part of the case ...
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Identification of other entities.

Given the following scenario, what three other entities (and their attributes) would be of importance to this model? SCENARIO: The transport authority in Jamaica has recently added train ...
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Employee permissions in ER model

I'd like to model an approach to permissions which I can visualise in code but am a little blurry about on the ER side of things; Each user will be logged in at this point and bound to a record ...
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How to model mappings at various levels

I'm trying to design the database model for my application and I'm finding it difficult to design the mappings for user access to various entities stored in the database. If access was only ...