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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 is primary key constraint?
Primary Key is a Constraint Used to avoid Duplicate entries in database table and you define primary key the column doesn't allow NULL values.
What is key constraints?
Primary Key is a Constraint Used to avoid Duplicate entries in database table and you define primary key the column doesn't allow NULL values.
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);
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.
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.
Have all tables primary key?
No, all tables do not have primary key. Primary must be explicitly defined and must not be null.
Can a primary key refer to a whole table?
No, a primary key do not refers to the whole table .A primary key refers to a field in the table that is not null and unique.
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.
