difference primary key and foreign key
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 NULLforeign key and primary key difference
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.Copyright © 2021 Codeinu
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