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A candidate key is a minimal superkey, [1] i.e., a superkey that doesn't contain a smaller one. Therefore, a relation can have multiple candidate keys, each with a different number of attributes. [2] Specific candidate keys are sometimes called primary keys, secondary keys or alternate keys.
Unique keys are an alternative to the primary key of the relation. In SQL, the unique keys have a UNIQUE constraint assigned to them in order to prevent duplicates (a duplicate entry is not valid in a unique column). Alternate keys may be used like the primary key when doing a single-table select or when filtering in a where clause, but are not ...
While a basic KSDS only has one key (the primary key), alternate indices may be defined to permit the use of additional fields as secondary keys. An alternate index (AIX) is itself a KSDS. The data structure used by a KSDS is nowadays known as a B+ tree. [10] [11]
A secondary chord is an analytical label for a specific harmonic device that is prevalent in the tonal idiom of Western music beginning in the common practice period: the use of diatonic functions for tonicization. Secondary chords are a type of altered or borrowed chord, chords that are not part of the music piece's key.
In the relational model of databases, a primary key is a designated attribute that can reliably identify and distinguish between each individual record in a table.The database creator can choose an existing unique attribute or combination of attributes from the table (a natural key) to act as its primary key, or create a new attribute containing a unique ID that exists solely for this purpose ...
In database design, a composite key is a candidate key that consists of two or more attributes, [1] [2] [3] (table columns) that together uniquely identify an entity occurrence (table row). A compound key is a composite key for which each attribute that makes up the key is a foreign key in its own right.
Keshon Gilbert scored 16 points, grabbed 10 rebounds and dished five assists as No. 3 Iowa State pulled away from No. 25 Baylor 74-55 in a Big 12 Conference showdown Saturday in Ames, Iowa.
Although the enharmonic key of A-flat major is preferred because A-flat major has only four flats as opposed to G-sharp major's eight sharps (including the F), G-sharp major appears as a secondary key area in several works in sharp keys, most notably in the Prelude and Fugue in C-sharp major from Johann Sebastian Bach's The Well-Tempered Clavier, Book 1.