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Is key and candidate key same?
Primary Key is a unique and non-null key which identify a record uniquely in table. A table can have only one primary key. Candidate key is also a unique key to identify a record uniquely in a table but a table can have multiple candidate keys.
Is AB a candidate key?
Yes, ABD is a candidate key. No subset of its attributes is a key.
Can candidate key name?
Both Primary Key and Candidate Key are the attributes that are used to access tuples from a table. These(Primary key and Candidate key) are also can be used to create a relationship between two tables. Here only ID can be primary key because the name, age and address can be same, but ID can’t be same.
Can primary key can be candidate key?
Primary key values should be unique and non-null. There can be multiple Super keys and Candidate keys in a table, but there can be only one Primary key in a table.
What is candidate key give example?
Candidate Key: The minimal set of attributes that can uniquely identify a tuple is known as a candidate key. For Example, STUD_NO in STUDENT relation. The value of the Candidate Key is unique and non-null for every tuple. For Example, STUD_NO is the candidate key for relation STUDENT.
Is candidate key a constraint?
It is because, in a table, we can have one or more than one candidate key, but we can create only one primary key for a table. However, if there is only one candidate key in a table, then it can be considered for both key constraints.
How are candidate keys calculated?
- The first step in the process of finding a normal form and decomposing a relation is to find the candidate. keys.
- R = (ABCDE), F = {A -> C, E -> D, B -> C}
- R = ABCDE, F = {A -> BE, C -> BE, B -> D}
- R = ABCDEF, F = {A -> B, B -> D, C -> D, E -> F}
- R = ABCD, F={AB -> C, BC -> D, CD -> A}
- R = ABCD, F={A -> BCD, C -> A}
Which is the only candidate key of the relation?
We conclude that AB can determine all the attributes of the given relation. Thus, AB is the only possible candidate key of the relation. Only one candidate key AB is possible. Remaining 3 attributes are non-essential attributes. Essential attributes will be definitely present in every key.
How to determine the essential attributes of a candidate key?
Step-01: 1 Determine all essential attributes of the given relation. 2 Essential attributes of the relation are- E, F and H. 3 So, attributes E, F and H will definitely be a part of every candidate key.
What do you call a set of candidate keys?
A set of minimal attribute (s) that can identify each tuple uniquely in the given relation is called as a candidate key.
How to determine the total number of candidate keys?
Let R = (A, B, C, D, E) be a relation scheme with the following dependencies- Determine the total number of candidate keys and super keys. Determine all essential attributes of the given relation. So, attributes A and B will definitely be a part of every candidate key.