a) Hyper data
b) Tera data
c) Meta data
d) Relations
Primary Key
A primary key is a unique identifier for a record in a database table.
Imagine a table of students. Each student has a unique student ID number. This student ID would be the primary key because it uniquely identifies each student record.
Key characteristics of a primary key:
- Unique: No two records can have the same primary key value.
- Not Null: Every record must have a primary key value.
- Minimal: It should contain only the necessary columns to uniquely identify a record.
Purpose:
- To efficiently locate specific records.
- To establish relationships between tables (foreign keys).
- To maintain data integrity.
By using primary keys, a database system can quickly find, update, or delete specific records without confusion or errors.