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In SQL, is it composite or compound keys?
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sqlcompoundkeyscomposite
Problem
About SQL (Computing/Databases):
When we have two or more fields in a table that, together, identify its records uniquely, what's the proper way of calling them? Composite or compound keys?
I've seen on the web both uses so I'm not really sure.
When we have two or more fields in a table that, together, identify its records uniquely, what's the proper way of calling them? Composite or compound keys?
I've seen on the web both uses so I'm not really sure.
Solution
Both composite key and compound key describe a candidate key with more than one attribute. According to the Relational Database Dictionary (C.J.Date) they mean the same thing.
In ER modelling the term "compound key" also has a more specific meaning. It means a key whose constituent attributes are references to keys in other entities - i.e. a compound key forms an identifying relationship. For most purposes, this isn't an especially useful or important concept so the terms composite/compound are often treated as interchangeable. It's probably best to stick to "composite key" unless you are referring specifically to the ER modelling concept of a compound key.
In ER modelling the term "compound key" also has a more specific meaning. It means a key whose constituent attributes are references to keys in other entities - i.e. a compound key forms an identifying relationship. For most purposes, this isn't an especially useful or important concept so the terms composite/compound are often treated as interchangeable. It's probably best to stick to "composite key" unless you are referring specifically to the ER modelling concept of a compound key.
Context
StackExchange Database Administrators Q#3134, answer score: 40
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