Can we have more than one NULL in a column having unique constraint?

Categories >> Software >> Databases >> SQL Server
Suggest New Category

Can we have more than one NULL in a column having unique
constraint?

Question Posted / srikanth

12 Answers
13743 Views
247Customer, I also Faced
E-Mail Answers

Answers were Sorted based on User's Feedback

Can we have more than one NULL in a column having unique constraint?..

Answer / kalu

No, because Unique constraint accepts only one null value.

Is This Answer Correct ?

16 Yes

3 No

Can we have more than one NULL in a column having unique constraint?..

Answer / saurabh

Is This Answer Correct ?

11 Yes

5 No

Can we have more than one NULL in a column having unique constraint?..

Answer / p.prabhu

No we cant have More than One Null in a column which is
having Unique Key Constraint. Because Unique Key Constraint
means having a value only once in the column.

Is This Answer Correct ?

4 Yes

1 No

Can we have more than one NULL in a column having unique constraint?..

Answer / santhoshkumar.k

No we can not have that option in sql server

Is This Answer Correct ?

4 Yes

2 No

Can we have more than one NULL in a column having unique constraint?..

Answer / krishnaraj p n

UNIQUE constraints can accept NULL just once. If the
constraint is defined in a combination of fields, then
every field can accept NULL and can have some values on
them, as long as the combination values is unique.

Is This Answer Correct ?

2 Yes

0 No

Can we have more than one NULL in a column having unique constraint?..

Answer / manoj pandey

No this is not possible... columns with Unique constraint
can only contain 1 null value/row.

@Manish... could you please try this:

create table #tempTable (id int, name varchar(50) unique)

insert into #tempTable
select 1, 'manoj' union
select 2, null union
select 3, null union
select 4, 'pandey'

Is This Answer Correct ?

1 Yes

0 No

Can we have more than one NULL in a column having unique constraint?..

Answer / maneesh

Yes there can be any number of NULLs.
Remember NULL <> NULL.

So uniqueness will still be there.

Just try it out.

Maneesh

Is This Answer Correct ?

6 Yes

6 No

Can we have more than one NULL in a column having unique constraint?..

Answer / habibur rahaman

It depends upon the database on which you are working.....in SQL we can have only one value but in oracle we can have n no of values.......i did it practically.

Is This Answer Correct ?

0 Yes

0 No

Can we have more than one NULL in a column having unique constraint?..

Answer / sasikumar

It is possible in Oracle database (NULL <> NULL) but not
possible in SQL server.

Is This Answer Correct ?

1 Yes

1 No

Can we have more than one NULL in a column having unique constraint?..

Answer / drona

UNIQUE constraints can accept NULL just once.
I have a dought?
Every null is different?

Is This Answer Correct ?

0 Yes

0 No

Post New Answer