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No unique can not be nulll....unique must have any unique value for unique identification.,...
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What is a primary key that is null?
Unique key
What not a likely primary key?
A field that is not unique and null can not be used as a primary key. Praimary key must satisfy the conditions of not null and unique.
What are the advantage of primary key?
Primary key that is used to identify a record uniquely. Primary key is a key that always unique and not null. A system generated primary key is called surrogate key.Primary key is the one which is always unique and not null. Advantage of primary key that it helps in identifying a tuple uniquely.
Can a primary key have a blank or null value entered into its cell?
No. A Primary Key is the Unique identifier and cannot be null and cannot be duplicate.
How you create or assign primary key?
A primary key is never null and is also unique . Example of primary key is create table emp (ecode integer NOT NULL PRIMARY KEY);
Can you use more than one null value for unique key?
No.
Features of primary key?
* In NOT NULL constraint the particular data cannot be NULL,* In UNIQUE constraint the same thing cannot be repeated, it must be unique,* The primary key is simply the combination of both these constraints.
What does the primary key in a data base do?
We know that primary key is the one that is not null and is always unique. A primary key uniquely identifies a record in a table.
Is a primary key a unique identifier?
NO, unique identifier allows null values.. so u dont called as primary key... primary key means it doesn't allow null n repeated values.... so we dont call unqiue identifier is a primary key...
What are properties of a primary key?
The properties of primary key are as follows: 1. It should be unique. 2. It should be not null.
Candidate key and primary key differnece?
All Primary keys are definitely Candidate Keys. A Candidate key is one which can be used as a Primary key that is not null and unique. That is one of the candidate keys can be chosen as a primary key.A Candidate key is a Unique Key and it can be used to find out any particular Tuple (row) in a table. The following are the differences between A Candidate key and a Primary Key: 1) A Unique key can be null but not a Primary key 2) On a table we can have only 1 primary key but 'N' number of unique keys.
What is the difference between primary key and unique index?
Primary key is a type of unique index with no null constraint on the columns involved. There can only be one Primary key whereas you can create other unique indexes on the table.
