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ER Diagram Notes
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| ## ER Diagrams ## | |
| triangle - ISA | |
| rectangle - entity | |
| oval - attribute | |
| diamond - relation | |
| [A] -> <B> : Key Constraint. Each entity in A uniquely identifies a relation in B | |
| [A] -> <B> <- [C] : 1:1 | |
| [A] -> <B> - [C] : many:1 | |
| [A] - <B> <- [C] : 1:many | |
| [A] - <B> - [C] : many:many | |
| [A] == <B> : Participation constraint. Each entity in A must be represented in relation B | |
| [[A]] ==> <<B>> - C : A is a weak entity related to parent entity A via relation C | |
| ---------- | |
| == is a thick line, | |
| [[A]] is a thick line entity, | |
| <<B>> is a thick line relation |
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