Table of Contents
- 1 What is the difference between a candidate key and primary key?
- 2 What is the difference between a key and super key Why do we designate one of the candidate keys of the relation to be a primary key?
- 3 Can a primary key be a candidate key?
- 4 Is super key same as primary key?
- 5 What is primary key and candidate key in SQL Server?
- 6 What is the difference between primary and alternate keys in MySQL?
What is the difference between a candidate key and primary key?
Primary Key is a unique and non-null key which identify a record uniquely in table. Candidate key is also a unique key to identify a record uniquely in a table but a table can have multiple candidate keys.
What is a super key in relational database?
Super key is a single key or a group of multiple keys that can uniquely identify tuples in a table. Super Key can contain multiple attributes that might not be able to independently identify tuples in a table, but when grouped with certain keys, they can identify tuples uniquely.
What is the difference between a key and super key Why do we designate one of the candidate keys of the relation to be a primary key?
Because regardless of how many candidate keys a relation may have, only one field can actually be used as the primary key for a given table. So designating a primary key is forcing you into choosing the one value – among all possibilities – that will determine a unique row in your table.
Is Candidate key a super key?
Super Key is an attribute (or set of attributes) that is used to uniquely identifies all attributes in a relation. Candidate Key is a subset of a super key. All super keys can’t be candidate keys. But all candidate keys are super keys.
Can a primary key be a candidate key?
Each Candidate Key can qualify as Primary Key. Primary Key – A Primary Key is a column or a combination of columns that uniquely identify a record. Only one Candidate Key can be Primary Key.
Is Super key a primary key?
The super key is a primary key with additional attributes, this extra information is used to uniquely identify an instance of the entity set. A candidate key is the most minimal subset of fields that uniquely identifies a tuple. Yes we can simply say that a candiate key is primary key but it must be unique.
Is super key same as primary key?
Difference between Super Key and Primary Key: Super Key is an attribute (or set of attributes) that is used to uniquely identifies all attributes in a relation. Primary Key is a minimal set of attribute (or set of attributes) that is used to uniquely identifies all attributes in a relation.
Is every primary key is a candidate key?
What is primary key and candidate key in SQL Server?
Primary Key – is a column or group of columns in a table that uniquely identify every row in that table. Candidate Key – is a set of attributes that uniquely identify tuples in a table. Candidate Key is a super key with no repeated attributes.
What is the difference between candidate keys and super keys?
Super key is a single key or a group of multiple keys that can uniquely identify tuples in a table. Super keys can contain redundant attributes that might not be important for identifying tuples. Candidate keys are a subset of Super keys. They contain only those attributes which are required to uniquely identify tuples.
What is the difference between primary and alternate keys in MySQL?
Primary key is a Candidate key chosen to uniquely identify tuples in the table. 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. Alternate keys are those Candidate keys that were not chosen to be the Primary key of the table.
What is a primary key in DBMS?
Primary Key is a minimal set of attribute (or set of attributes) that is used to uniquely identifies all attributes in a relation. 2. All super keys can’t be primary keys. Primary key is a minimal super key.