0
Why do you designate one of the candidate key of relation to be the primary key?
Wiki User
∙ 10y ago
We designate one of the candidate key of a relation to be a primary key because that primary key is use for any foreign key references.
Wiki User
∙ 10y ago
Add your answer:
Earn +20 pts
What is the prime attribute in DBMS?
prime attributes are the attributes of a candidate key which will give uniqueness. a candidate key is (the subset of superkey) which gives uniqueness. Super key is the maximum set of attributes that can provide uniqueness example ABCDE is a super key AB CD DE are the candidate keys s.t. AB is the primary key. CD and DE are the secondary/alternate keys.
What is a primary key what is its purpose and why do you use it?
A primary key is a unique identifier for each record in a database table. Its purpose is to ensure the uniqueness and integrity of the data within the table. It is used to uniquely identify each row, which allows for efficient data retrieval and modification, as well as establishing relationships between tables through foreign keys.
Can super key be as primary key?
I think super key is treated as the primary key because in a table their will be only one primary key.
What are the importance of primary key?
Importance of primary key
What are the advantage of primary key?
Primary key that is used to identify a record uniquely. Primary key is a key that always unique and not null. A system generated primary key is called surrogate key.Primary key is the one which is always unique and not null. Advantage of primary key that it helps in identifying a tuple uniquely.
What is candidate key in dbms?
more than one primary key to identify the record uniquely is called candidate key.
Candidate key and primary key differnece?
All Primary keys are definitely Candidate Keys. A Candidate key is one which can be used as a Primary key that is not null and unique. That is one of the candidate keys can be chosen as a primary key.A Candidate key is a Unique Key and it can be used to find out any particular Tuple (row) in a table. The following are the differences between A Candidate key and a Primary Key: 1) A Unique key can be null but not a Primary key 2) On a table we can have only 1 primary key but 'N' number of unique keys.
What is the difference between primary key and candidate key?
Candidate Key is used to uniquely identify the records of a table. An attribute becomes a Primary Key, if all the other candidate keys lose race for being qualified as Primary Key.
How do you find candidate key in a relation?
have sex
Explain two rules in relational model of database systems?
1) Entity Integrity: In a base relation, no attribute of a primary key can be null. 2) Referential Integrity: If foreign key exists in a relation, either foreign key value must match a candidate key value of some tuple in its home relation or foreign key value must be wholly null
What are the requirements for a relation to be in Second Normal Form?
A relation is in second normal form (2NF) if any of the following conditions apply: The primary key consists of only one attribute No non-primary key attribute exists in the relation Every non-primary key attribute is functionally dependent on the full set of primary key attributes
All types of keys in database?
* Alternate key - An alternate key is any candidate key which is not selected to be the primary key * Candidate key - A candidate key is a field or combination of fields that can act as a primary key field for that table to uniquely identify each record in that table. * Compound key - compound key (also called a composite key or concatenated key) is a key that consists of 2 or more attributes. * Primary key - a primary key is a value that can be used to identify a unique row in a table. Attributes are associated with it. Examples of primary keys are Social Security numbers (associated to a specific person) or ISBNs (associated to a specific book). In the relational model of data, a primary key is a candidate key chosen as the main method of uniquely identifying a tuple in a relation. * Superkey - A superkey is defined in the relational model as a set of attributes of a relation variable (relvar) for which it holds that in all relations assigned to that variable there are no two distinct tuples (rows) that have the same values for the attributes in this set. Equivalently a superkey can also be defined as a set of attributes of a relvar upon which all attributes of the relvar are functionally dependent. * Foreign key - a foreign key (FK) is a field or group of fields in a database record that points to a key field or group of fields forming a key of another database record in some (usually different) table. Usually a foreign key in one table refers to the primary key (PK) of another table. This way references can be made to link information together and it is an essential part of database normalization
How much types of keys are available in dbms?
There are five types of keys in database management system . The name of the five keys are as follows .:1) surrogate key -which is the system generated primary key .2) Primary key - same function as surrogate key but user defined.3) candidate key -combination of two more keys.4) alternate keys - alternative for candidate keys.5) foreign key - primary key of another table.There are five types of keys in database management system.These five keys are surrogate, primary, candidate, alternate, foreign keys .
What is the difference between primary key and secondary key in database?
A primary key is a unique identifier for each record in a database table and is used to ensure data integrity and enforce entity integrity. A secondary key, also known as a candidate key, is an alternate unique key that can be used to identify records, but is not designated as the primary key.
Difference between a super key and a candidate key?
Different set of attributes which are able to identify any row in the database is known as super key. And minimal super key is termed as candidate key i.e. among set of super keys one with minimum number of attributes. Primary key could be any key which is able to identify a specific row in database in a unique manner.
What are the differences between super key primary key candidate key and foreign key?
Super key: A set of attributes that uniquely identifies a tuple in a table. Primary key: A specific super key chosen to uniquely identify each tuple in a table and must be unique and not null. Candidate key: Any super key that could be chosen as the primary key. Foreign key: A field in a table that is a primary key in another table, used to establish a relationship between the two tables.
How can you apply the primary key?
Primary key is the one which is uniquely defined in the attributes of a table. It can be used to pull any kind of data regarding a particular tuple in the table. PRIMARY IS ALSO A CANDIDATE KEY.
