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Vault sync: 2021-10-25 17:11:26

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Nick Leeman 2021-10-25 17:11:27 +02:00
parent 0f8042c145
commit 82e4323af3
3 changed files with 12 additions and 6 deletions
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.obsidian/workspace vendored
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@ -9,7 +9,7 @@
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School/Development/Foreign Key.md
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# Foreign Key # Foreign Key
A Foreign key is a [[Constraint]] that protects links between tables. Foreign key is a attribute or attributes that link to the [[Primary Key]] of a other entity set (table). A Foreign key is a [[Constraint]] that protects links between tables. Foreign key is a attribute or attributes that link to the [[Primary Key]] of a other entity set (table).
For ## Example
|ID (PK)|Name|Age|Sex|Length|
|-----|-----|-----|-----|-----|
|1|Nick|21|M|190|

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School/Development/Primary Key.md
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@ -5,4 +5,8 @@ There can only be ONE primary per table and can consist of multiple attributes (
A primary key is **not** required, but highly advised. Even if you don't use it its better to include one in your schema. A primary key is **not** required, but highly advised. Even if you don't use it its better to include one in your schema.
## Exaple ## Example
**Name (PK) - Age - Sex - Length**
In the table schema above, only one entity where the name is Nick can exist because Name is the primary key.