primary key vs 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 NULLwhat is foreign key
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 tableprimary key vs 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.What is foreign key?
Foreign Key is a non-key attribute which is derived from the primary key
of another table which links those tables together.difference between primary key and foreign key
primary key and foreign keyCopyright © 2021 Codeinu
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