Answer / viresh rajput

primary key:- The attribute or combination of attributes
that uniquely identifies a row or record.

Foreign Key:- an attribute or combination of attribute in a
table whose value match a primary key in another table.

Composite key:- A primary key that consistsof two or more
attributes is known as composite key

candidate key:-A candidate key uniquely identifies the rows
in a table.there can be more than 1 candidate key in a
table, in which one should be a primary key.


Alternate Key:- Any of the candidate keys that is not part
of the primary key is called an alternate key.

Answer / sonya jalil khan

candidate key:if it qualifies to uniquely select a specific
row in the table such that the data in that table depend
completely on that key and nothing else is required.the
candidate key cannot hold NULLS.the candidte key should
never change it must holds the same value for a given
occurence of an entity for the lifetime of that
entity.
example:
EMP ID , NAME,JOB,DEPARTEMENT ID
here emp id is a candidate key.becouse a minimal set of
columns that can be used to identify a single row

Answer / mona

A set of fields that uniquely identifies a tuple according
to a key constraint is called candidate key for the relation.
(1)No two values of keys are same
(2)the set of fields{sid,sname} is not a key for
students,because this set properly contains the key{sid}.
The set {sid,sname} is an example of a super key,which is a
set of fields that contains a key.
EX:
create table customer(customer_name char(20),street
char(30),city char(30),primary key(customer_name));

Answer / shiv om mishra

candidate key- is a combination of two attributes taht can be uniquely used to identify a datbase record without any extraneous data.
Each table may have one or more candidate key.
A candidate key of a relation tells us all teh set of all its attribute is a superkey.

Answer / priyanka vaydande

What do u mean by different attributes?..it can be like
student id and course id which are two different
attributes..yet they form a primary key??

Answer / rajneesh

primary key: should be unique and Not Null
Unique Key: accept 1 null value and unique

Answer / jeff

A candidate key is able to identify a unique tuple in a
relation through an attribute or attribute set.

A foreign key makes sure that a tuple in a relation does
not match a tuple in another relation which does not exist

Answer / divya lover

candidate key: is a column in a table which has thhe ability
to become a primary key.

alternate key:any of the candidate key that is not part of
the primary key. cheating of my lover divya......

Answer / nnnn

Candidate Key.....???? Help me out..!!!!!

Answer / ramesh

A composite Key can be either Primay or Unique Key
More then One Key columns are said to be composite keys

Candidate Key(Primary Key) is a Key which Maintains the Row
Uniue .Can be defined based on the Entity


Alternate Key or Unique Key is similar to PK ,except it
accepts null Values .So that the records can still be
entered submitting null values to this attribute.

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