Determinants determine the values assigned to other attributes
A qualifier in a database table is an attribute that can be used to determine the values assigned to other attributes in the same row. By this definition, any primary or candidate key is a determinant, but there may be determinants that are not primary or candidate keys.
For example, a company can use a table of attributes, and .
123 td> |
Megan TD> | Brown TD> | 29/01/1979 TD> TR> |
234TD> | Ben TD> | Wilder TD> | 14/02/1985TD> TR> |
345TD> | Megan TD> | Chowdery TD> | 14-2-1985TD> TR> |
456TD> | Charles TD> | Brown TD> | 19/07/1984TD> TR> table>
Deterministic relationships with database keys In this example, these are the determinant, the candidate key, and also the primary key. This is a candidate key because searching the entire database for 234 returns a row of information about Ben Wilder and no other entries are shown. Another candidate key comes up when searching the database for information in three columns; and, which also gets the same result. It is a primary key because of all combinations of columns that can be used as a candidate key, it is the easiest column to use as a primary reference to this table. It is also guaranteed to be unique to this table, regardless of the number of other employees, unlike the information in the other columns.
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