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There is two difference between them. 1. The not null constraint is by default added to primary key, it means, primary key attribute cannot accept null values, whereas, the attribute declared as unique can accept null values. It is the major difference between the two. 2. Secondly, we can have only one primary key in a relation, whereas, multiple attributes can be declared unique at the same time.
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What is the difference between a Primary Key and a Secondary Key?
A Primary Key is a unique identifier for each record in a database table and is used to enforce entity integrity. A Secondary Key is a non-unique index that is used for querying and organizing data efficiently but does not have the constraint of uniqueness.
What is the key difference between a primary and secondary amine in terms of their chemical properties and reactivity?
The key difference between a primary and secondary amine is the number of carbon atoms attached to the nitrogen atom. In a primary amine, there is one carbon atom attached to the nitrogen, while in a secondary amine, there are two carbon atoms attached. This difference affects their chemical properties and reactivity. Primary amines are more reactive than secondary amines because the lone pair of electrons on the nitrogen atom is more available for reactions in primary amines.
What is the difference between primary key and secondary key in database?
The primary key is the field containing unique values that aid in database operations. The secondary key is used in addition or as an alternate to the primary key. Both are candidate keys, it's just that one was chosen to be primary.
What is the difference between a candidate key an a secondary key?
A candidate key is a unique key that can uniquely identify each record in a database table, whereas a secondary key is a non-unique key used for data retrieval and indexing purposes. Candidate keys can be chosen as the primary key for the table, while secondary keys provide alternate ways to access and organize the data.
What the difference between primary key and scendary key?
A primary key is a unique identifier for a record in a database table and is used to ensure each record is uniquely identifiable. A secondary key is a key used for sorting and indexing purposes, but can have duplicate values within a table.
What is stored as primary key in a second table?
a secondary key
Differentiate between primary secondary and foreign keys?
Primary key uniquely identifies each record in a database table and must have a unique value for each record. Secondary key is a field that can be used to uniquely identify a record, but it is not the primary key. Foreign key is a field in a table that links to the primary key of another table, establishing a relationship between the two tables.
What is the difference between a primary key and a foreign key?
A primary key uniquely identifies each record in a table and ensures data integrity. A foreign key establishes a relationship between two tables, referencing the primary key of another table to enforce referential integrity.
What is the difference between primary key and candidate key?
Candidate Key is used to uniquely identify the records of a table. An attribute becomes a Primary Key, if all the other candidate keys lose race for being qualified as Primary Key.
Primary and secondary key in c and c plus plus?
There are no "primary and secondary keys" in c and c plus plus.
What key defines a relationship between two tables 1 Primary key 2 Secondary key 3 Foreign key?
Foreign key is used to define a relationship between two tables by referencing the primary key of another table. It ensures data integrity and enforces referential integrity between the related tables.
What is secondary indexes in dbms?
secondary index is a key which is created other than primary key, to speed up processing.
