Can we use more than one null value for unique key?
Answer Posted / amit rajoria
Yes, we can use multiple Null values in case of Unique Key
Column. This is one the main difference between Unique Key
and Primary Key that Unique Key always allows multiple
entries of Null Statement where as Primary Key never allows
this.
I am hereby giving you a very very basic example which
suggests that Unique Key can have more than one Null
Statement :-
SQL> create table abcd(name varchar2(10) unique);
Table created.
**********************
Now insert the values :-
SQL> insert into abcd(name)values('amit');
1 row created.
SQL> insert into abcd(name)values('ami');
1 row created.
SQL> insert into abcd(name)values(null);
1 row created.
SQL> insert into abcd(name)values(null);
1 row created.
SQL> insert into abcd(name)values(null);
1 row created.
SQL> commit;
Commit complete.
SQL> select * from abcd;
NAME
----------
amit
ami
Here blank space above represents the entries of null
statements..!!
Is This Answer Correct ? | 14 Yes | 3 No |
Post New Answer View All Answers
what is sql in mysql? : Sql dba
How do you modify a trigger?
What does inner join mean?
Which data type is a composite type?
what is dbms? : Sql dba
What is a ddl command?
How do I enable sql encryption?
What is relationship? How many types of relationship are there?
What is the difference between cross join and natural join?
Explain what is table in a database?
Is primary key clustered or nonclustered?
What is schema in sql?
What is the difference between microsoft access and sql?
what is the use of double ampersand (&&) in sql queries?
What is rollback?