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Fix docs for ER diagrams #1346

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merged 2 commits into from
Apr 10, 2020
Merged

Fix docs for ER diagrams #1346

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91b6479
Escape the pipes in the syntax table
spopida Apr 10, 2020
3db27e6
Tiny tweaks to docs for ER diagram
spopida Apr 10, 2020
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10 changes: 5 additions & 5 deletions docs/entityRelationshipDiagram.md
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Expand Up @@ -2,7 +2,7 @@

> An entity–relationship model (or ER model) describes interrelated things of interest in a specific domain of knowledge. A basic ER model is composed of entity types (which classify the things of interest) and specifies relationships that can exist between entities (instances of those entity types). Wikipedia.

Note that practitioners of ER modelling almost always refer to entity types simply as entities. For example the CUSTOMER entity type would be referred to simply as the CUSTOMER entity. This is so common it would be inadvisable to do anything else, but technically an entity is an abstract *instance* of an entity type, and this is what an ER diagram shows - abstract instances, and the relationships between them. This is why entities are always named using singular nouns.
Note that practitioners of ER modelling almost always refer to *entity types* simply as *entities*. For example the CUSTOMER entity type would be referred to simply as the CUSTOMER entity. This is so common it would be inadvisable to do anything else, but technically an entity is an abstract *instance* of an entity type, and this is what an ER diagram shows - abstract instances, and the relationships between them. This is why entities are always named using singular nouns.

Mermaid can render ER diagrams
```
Expand All @@ -24,7 +24,7 @@ Relationships between entities are represented by lines with end markers represe

## Status

ER diagrams are a new feature in Mermaid and are **experimental**. There are likely to be a few bugs and constraints, and enhancements will be made in due course.
ER diagrams are a new feature in Mermaid and are **experimental**. There are likely to be a few bugs and constraints, and enhancements will be made in due course. Currently you can only define entities and relationships, but not attributes.

## Syntax

Expand Down Expand Up @@ -61,10 +61,10 @@ Cardinality is a property that describes how many elements of another entity can

| Value (left) | Value (right) | Meaning |
|:------------:|:-------------:|--------------------------------------------------------|
| `|o` | `o|` | Zero or one |
| `||` | `||` | Exactly one |
| `\|o` | `o\|` | Zero or one |
| `\|\|` | `\|\|` | Exactly one |
| `}o` | `o{` | Zero or more (no upper limit) |
| `}|` | `|{` | One or more (no upper limit) |
| `}\|` | `\|{` | One or more (no upper limit) |

### Identification

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