ITPEC IP April 2026 Question 26

Elimination of redundancy and inconsistency of data — normalisation splits tables so that each fact is stored in only one place.

In an unnormalised table the same fact, such as a customer's address, is repeated on many rows. Updating some copies but not others leaves the data contradicting itself (an update anomaly), and facts can be impossible to add or can be lost with a deletion. Normalisation divides the table along the dependencies between items, so each fact is held once and a change is made in one place.

Answer (c)

Why not others:

• •(a) — compatibility between different types of computers depends on data formats and standards, not on table design
• •(b) — compression encodes data in fewer bits; normalisation changes the table structure and can even add tables and keys
• •(d) — backups guard against device failure, which a normalised database suffers like any other

Key rule: Normalisation is about the logical design (one fact, one place); physical concerns such as compression, compatibility and backup are handled separately.

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