Thread by @meetjain74

Types of keys in SQL

A thread🧵

📌Primary key
A primary key is a table attribute or column that identifies every record present in a table uniquely. There can be only one primary key attribute in a table and primary key column attributes can't be the same or null values.

📌Super key
It is the set of all columns which helps to identify rows in a table uniquely.

📌Candidate key
The candidate key is a column or set of columns that can qualify as a primary key in the database. There can be multiple candidate keys in a table and only one candidate key can qualify as a primary key.

📌Composite key
It is the set of two or more attributes that helps to identify each tuple in a table uniquely. Any key such as super, primary, candidate key, etc can be called a composite key if it has more than one attribute.

📌Foreign key
The foreign key is a key used to link two tables together. This is also called as referencing.

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