Interested to Buy Any Domain ? << Click Here >> for more details...
IN A TABLE HAVE ONE COLUMN PRIMARY KEY..IT WILL NOT ALLOWS
NULL VALUES AND DUPLICATE VALUES..INSTEAD OF PRIMARY KEY
WHY CANT WE USE UNIQUE AND NOT NULL.THESE TWO ALSO DOESNT
ACCEPT NULL VALUES IN NOT NULL AND UNIQUE DOESNT ACCEPT
DUPLICATE VALUES?
SO WHAT IS THE DIFEERENCE BETWEEN(UNIQUE,NOT NULL) AND
PRIMARY KEY??????
- 8 Answers
- 10377 Views
- rsystems, I also Faced
- E-Mail Answers
Answer Posted / aritra biswas
With the creation of primary key the oracle server
automatically creates and maintains a index on the primary
key column(s). Because of that index, the searching
processes on that table will be very fast where as
declaring a column as a (unique+not null) will not create
any index on that colum(s).It has to be created manually by
the DBA/users if we wish to enhance the searching process.
| Is This Answer Correct ? | 8 Yes | 7 No |
Post New Answer View All Answers
What is parallel hint?
How can we make an if statement within a select statement?
Why stored procedure is better than query?
What is a rank in sql?
Is mariadb a nosql database?
What is rank () in sql?
Do foreign keys improve performance?
What is group function in sql?
What is difference between left and right outer join?
Do triggers have restrictions on the usage of large datatypes, such as long and long raw?
Are pl sql variables case sensitive?
can sql servers linked to other servers like oracle? : Sql dba
How is sql used in oracle?
How will you distinguish a global variable with a local variable in pl/sql?
define sql insert statement ? : Sql dba
