Last post Aug 04, 2016 02:23 PM by Chris Zhao
Aug 01, 2016 05:21 PM|salim20001|LINK
Hi, I'm trying to complete these keys.
Aug 01, 2016 08:40 PM|march11|LINK
you are missing 2 other key words, Index and foreign.
Aug 02, 2016 07:09 AM|balu.devara|LINK
clustered index and foreign key
Aug 04, 2016 02:23 PM|Chris Zhao|LINK
Following is the list of Keys.
1. Super Key
Super key is a set of one or more than one keys that can be used to identify a record uniquely in a table. Example : Primary key, Unique key, Alternate key are subset of Super Keys.
2. Candidate Key
A Candidate Key is a set of one or more fields/columns that can identify a record uniquely in a table. There can be multiple Candidate Keys in one table. Each Candidate Key can work as Primary Key.
3. Primary Key
Primary key is a set of one or more fields/columns of a table that uniquely identify a record in database table. It can not accept null, duplicate values. Only one Candidate Key can be Primary Key.
4. Alternate key
A Alternate key is a key that can be work as a primary key. Basically it is a candidate key that currently is not primary key.
5. Composite/Compound Key
Composite Key is a combination of more than one fields/columns of a table. It can be a Candidate key, Primary key.
6. Unique Key
Uniquekey is a set of one or more fields/columns of a table that uniquely identify a record in database table. It is like Primary key but it can accept only one null value and it can not have duplicate values.
7. Foreign Key
Foreign Key is a field in database table that is Primary key in another table. It can accept multiple null, duplicate values.