Answer / naresh

Primary key:it can not be null

Unique:it can have only one null value in a table.

Answer / thaqi

unique key: allows NULL values and doesn't allow duplicate
values.

primary key:doesn't allow both NULL and duplicate values

Answer / sivasankar k.c

Primary key: it is clustered index. it not allows null
values. Only one primary in each table.

Unique Key: it is non clustered index. Unique key allows
null values.its allows only one null value. More than one
unique key in table.

Answer / navneet sharma

Unique key allow null value and it is a non cluster index
Primary key does not allow null value and it is custer index

Answer / hari

Primary key : Doen't allow null values
Unique key : allow one null value
Primary key create cluster index
Unique Key create non-cluster index

Answer / suresh kaudi

Primary Key: Not allow null values,when we make primary key
automatically create cluster index,primary key we make
other foreign key.

Unique key: allow one null value,we can't make it foreign
key to other table.here we cane make only non-cluster index

Answer / sunil kumar mishra

Primary key is a particular coloum that is unique in every
tuple is called primary key and ofenly it does not support
null values since it is used to uniquely identitfy row in a
table(Relation) and automatically does go to replace into
clustered index and support distinct value and Each table
should have a primary key, and each table can have only one
primary key.(Primary keys must contain unique values)

Unique value-
Unique values is same, in some manner, primary key since
You can have many UNIQUE constraints per table but primaty
key kan have one in each table.it support nonClustered
index.

Answer / suresh kaudi

Primary key : Not Accept null values
Unique key : Accept Onley one null value
When you Make Primary key In a table cluster index create
Automatically mean default.
Unique Key create Automatically non-cluster index

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here id col have primary key and identity id name 1 a 2 b 3 c 4 d delete 2nd row then o/p will be id name 1 a 3 c 4 d next inssert 2nd row and i want o/p will be id name 1 a 2 e 3 c 4 d

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