Superkey
A superkey is a set of one or more attributes whose values uniquely identify each row in a relation, whether or not the set is minimal.
100 SQL Server Mistakes and How to Avoid Them
A super key is a set of attributes that uniquely identifies every row in a relation, whether or not it is minimal.
- How it is used
- Uses superkeys to test row uniqueness while selecting keys during first normal form normalization.
- How deep it goes
- Defines superkeys and minimal candidate keys, then works through single-attribute and composite identification cases.
- Examples
- Uses Sales Order Number, Purchase Order Number, and a Product Name plus Product Type Name pair.
- What you can do after
- Evaluate/understand whether one attribute or a combination uniquely identifies each relation row.
Read how 100 SQL Server Mistakes and How to Avoid Them explains superkey →
Grokking Relational Database Design
A superkey is a set of one or more table columns whose values uniquely identify a row, possibly including unnecessary columns.
- How it is used
- Defines unique row identification while supporting primary-key selection and database normalization.
- How deep it goes
- Explains uniqueness, unnecessary columns, minimality, and key hierarchy but stops short of detailed dependency analysis.
- Examples
- Uses purchase_id and payment_id as surrogate primary-key examples for purchase and payment_method tables.
- What you can do after
- Evaluate whether a set of columns uniquely identifies rows and distinguish superkeys from minimal candidate keys.
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Related concepts
- candidate keyincludes · A candidate key is a minimal set of attributes whose values uniquely identify each row in a relational relation.
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