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That is, non-key attributes are functionally dependent on the superkey. The set of all attributes is always a superkey (the trivial superkey). Tuples in a relation are by definition unique, with duplicates removed after each operation, so the set of all attributes is always uniquely valued for every tuple.
The name is a three-letter acronym for DataBase Manager, and can also refer to the family of database engines with APIs and features derived from the original dbm. The dbm library stores arbitrary data by use of a single key (a primary key) in fixed-size buckets and uses hashing techniques to enable fast retrieval of the data by key.
A database management system (DBMS) is a computer program (or more typically, a suite of them) designed to manage a database, a large set of structured data, and run operations on the data requested by numerous users. Typical examples of DBMS use include accounting, human resources and customer support systems.
Download as PDF; Printable version; In other projects ... Super key may refer to : Super key (keyboard button) ... modifier key on keyboards; Superkey, database ...
For example if there is a table storing the information about US citizens, the Social Security Number would act as the natural key, Social Security Number being the natural key might pose a problem in the future if the US government changes the structure of the Social Security Number and increases the number of digits in the SSN due to some reason.
In relational database management systems, a unique key is a candidate key. All the candidate keys of a relation can uniquely identify the records of the relation, but only one of them is used as the primary key of the relation. The remaining candidate keys are called unique keys because they can uniquely identify a record in a relation.
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Berkeley DB (BDB) is an embedded database software library for key/value data, historically significant in open-source software. Berkeley DB is written in C with API bindings for many other programming languages. BDB stores arbitrary key/data pairs as byte arrays and supports multiple data items for a single key.