Databases
It is like…
A database table is like a class register
A relational table is like your lecturer's class register
Quick check · tap an answer to continue
Lesson notes
Key points
- Picture the register at UMaT: every student gets one row, and every column records the same kind of detail.
- Each row is a tuple, each column is an attribute, and your unique index number is the primary key.
- Here it breaks: a relation is a set, so row order means nothing and two identical rows can never exist.
Definitions
- Relation
- A set of tuples over the same attributes: unordered, with no duplicate rows.
Takeaway: Table = relation, row = tuple, column = attribute, ID = key.
Quick check: In the relational model, what does the order of rows in a relation mean?
- It sets the primary key
- It has no meaning at all
- It records insertion time
A relation is a set of tuples, and sets are unordered.
The registerThe mappingWhere it breaks
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