?????????????? ?????? and other keys
Susheel Kumar
Web Developer, App Developer, Software Developer, React, Node Js, Angular IO, Laravel
1. ?????????????? ??????
???- A unique identifier for each record in a table.
???- Cannot be null.
???- Ensures that each row is unique.
2. ?????????????? ??????
???- A field (or collection of fields) in one table, that refers to the Primary Key in another table.
???- The key to establishing relationships between tables.
3. ?????????????????? ??????
???- A combination of two or more columns to create a unique identifier for each record.
???- Useful when a single column isn’t enough to uniquely identify a record.
4. ?????????? ??????
???- A set of one or more columns that can uniquely identify a record.
???- A Primary Key is a special case of Super Key.
5. ?????????????????? ??????
???- A column, or set of columns, that can qualify as a Primary Key.
???- Unique and has the potential to become a Primary Key.
6. ???????????? ??????
???- Ensures uniqueness of the column or column combination.
???- Similar to Primary Key but can have one null value.
7. ?????????????????? ??????
???- A Candidate Key that is not the Primary Key.
???- Secondary option for a unique identifier.
8. ?????????????? ??????
???- A key that naturally occurs in the attributes of an entity, like an email address or a social security number.
9. ?????????????????? ??????
???- An artificial key created for a table when a natural, unique identifier isn’t available or suitable.
10. ?????????????????? ??????
???- Used for data retrieval purposes, not for identification.
???- Helps in creating non-clustered indexes.