Database Concepts

Every single-table database is made of three building blocks: fields, records and (usually) a primary key.

Fields

A field is one specific piece of information about each item; it appears in the table as a single column.

Examples of fields for a customer database: CustomerID, FirstName, LastName, DateOfBirth, PhoneNumber.

Records

A record is the collection of fields that all belong to one specific item; it appears in the table as a single row.

For the customers table, each customer is one record. If there are 200 customers, there are 200 records.

Easy way to remember: fields are columns, records are rows.

Primary keys

A primary key is a single field whose value is unique for every record in the table. It uniquely identifies each record so the database can tell one from another.

Examples:

• StudentID in a school students table.
• CarRegistration in a vehicles table.
• ProductCode in a shop's products table.
• MemberID in a club's members table.

A primary key cannot be left blank, and no two records can share the same primary-key value. This matters because the database needs an unambiguous way to refer to each record, especially when records are updated or deleted.

A worked example: a students table

In this table:

• The fields (columns) are StudentID, FirstName, LastName, MarkSubmitted, Percentage. There are 5 fields.
• Each row is a record for one student. There are 6 records.
• The primary key is StudentID because every student has a unique seven-digit ID.