A database is an organised collection of related data. In most databases the data is kept in one or more tables.
Records and fields
A table is a grid. Each row is a record holding all the data about one item, such as one student. Each column is a field holding one piece of data, such as Name or Age, for every record.
| StudentID | Name | Age |
|---|---|---|
| S01 | Aina | 15 |
| S02 | Ben | 14 |
Here each row is a record; StudentID, Name and Age are fields.
Key idea
Row = record (one item). Column = field (one attribute). The primary key is a field whose value is unique for every record, so no two records can share it.
The primary key
A primary key uniquely identifies each record. In the table above, StudentID is a good primary key because every student has a different ID. Name would be a poor key, because two students could share a name. When you search for one record, the primary key lets the database find exactly the right row with no confusion.
Storing data in tables like this has clear benefits over a plain list: the same data is not repeated, records are easy to search and sort, and each field can hold a fixed data type such as text for Name or a number for Age. This keeps the data neat and reliable.
Remember
- A record is a row; a field is a column.
- A primary key is unique and cannot repeat.
- A primary key value should not be left empty.