Answer :
A secondary key is defined as a key that is used strictly for data retrieval purposes.
Secondary data is data obtained from the results of previous studies. Generally, this type of data has information in the form of "referenced, quoted, or reported". This proves if the researcher does not get the data obtained from the main source.
Key Types in Relational Databases
In relational method, there are 6 known keys which will be explained as follows:
- Candidate Key, one of a series that has a unique value to distinguish or identify.
- Primary Key, attribute Is a candidate key that has been selected to uniquely identify each record.
- Alternate key, Unselected candidate key.
- Foreign Key, a collection of fields in one relation that is used to "refer" (point) to a row (tuple) in another relation (must correspond to the primary key in the second relation).
- Secondary key, an attribute or combination used only for data retrieval purposes.
- Composite key, a key consisting of 2 or more attributes that uniquely identify an entity occurrence.
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