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difference between primary key and foreign key

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Rasel Ahmed answered on December 5, 2020 Popularity 9/10 Helpfulness 3/10

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Primary Key:
1. It is used to uniquely identify data in the table
2. It can’t be null
3. Two or more rows can’t have same primary key
4. Primary has clustered index
5. Primary key constraint can be defined on temporary table

Foreign Key:
1. It is used to maintain relationship between tables
2. t can accept the null values
3. t can carry duplicate value for a foreign key attribute
4. By default, It is not clustered index
5. It can’t be defined on temporary tables

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Contributed on Jun 15 2022

Rasel Ahmed

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Primary Key :
It is unique column in every table in a database
It can ONLY accept;
    - nonduplicate values
    - cannot be NULL
Foreign Key: 
It is a column that comes from a different table and
using Foreign key tables are related each other
It is the primary key of another table
It can be duplicate or null for another table

Unique Key:
Only unique value and also can contain NULL

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Contributed on Dec 05 2020

Obedient Ocelot

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foreign key and primary key difference

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PrimaryKey:-

A primary key constrain is a column or group of columns that uniquely identifies every row in the table of the relational database management system. 
It cannot be a duplicate, meaning the same value should not appear more than once in the table.

Foreign key:-
A table can have more than one primary key. 
Primary key can be defined at the column or the table level.
If you create a composite primary key, it should be defined at the table level.
Foreign key is a column that creates a relationship between two tables. The purpose of the Foreign key is to maintain data integrity and allow navigation between two different instances of an entity. It acts as a cross-reference between two tables as it references the primary key of another table. 
Every relationship in the database should be supported by a foreign key.

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Contributed on Jul 12 2021

Mighty Unicorn

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difference between primary key and foreign key

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primary key and foreign key

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Contributed on Mar 24 2021

Good Gnu

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difference between primary key and foreign key

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