1NF

0 · Recall Warm-up

Answer from memory first. Answers are in the Answer Vault at the bottom.

1. What does dependency preservation require? from Lesson 4.3.2
2. What is the binary lossless test? from Lesson 4.3.1
3. Which relational property forbids a cell holding {Hindi, English}? from Lesson 2.1.1

1 · The Hook

Normal forms are a ladder: 1NF → 2NF → 3NF → BCNF (→ 4NF). Each step forbids one more kind of redundancy, and each higher form includes all lower ones. The first step is about the shape of values; the rest are about FDs. GATE's favourite question is "what is the highest normal form of R?", so you need the exact condition of each rung.

2 · Predict First

STUDENT(roll, name, phones) stores "98250 11111, 98980 22222" in one phones cell for Asha. Is this table in 1NF? How would you fix it?

Make a guess in your head. The answer opens Section 3.

3 · Core Concept

Predict First — the answer

Not in 1NF: a cell holds a set of values. Fix: a separate table STUDENT_PHONE(roll, phone) with one phone per row (the multivalued-attribute mapping of Lesson 2.4.1).

First normal form (1NF)

A relation is in 1NF if every attribute's domain contains only atomic (indivisible) values, and every cell holds a single value from that domain. No sets, lists, repeating groups or nested tables.

The relational model of Lesson 2.1.1 already assumes 1NF; "relation" in GATE questions means 1NF unless said otherwise.

Violations and fixes

Fix options for a multivalued attribute:

1. Separate table (preferred): STUDENT(roll, name), STUDENT_PHONE(roll, phone).
2. Expand rows: (roll, name, phone) with one row per phone; key becomes (roll, phone). Removes the 1NF problem but adds redundancy (name repeats), which 2NF will catch.
3. Fixed columns phone1, phone2: needs a maximum and leaves NULLs; poor design.

"Atomic" depends on use

A date "2026-10-26" is atomic if the database never needs its parts as values. Atomicity is about how the data is used: if queries keep extracting the month with string functions, the design should store parts separately.

What 1NF does not fix

ENROLL_INFO of Lesson 4.1.1 is in 1NF, yet full of anomalies. The next rungs, built on FDs and keys, deal with those.

4 · Visual

NOT 1NF                              1NF (separate table)
roll  name   phones                  STUDENT(roll, name)      STUDENT_PHONE(roll, phone)
1     Asha   {98250..., 98980...}    1  Asha                  1  98250...
2     Bhavin {94260...}              2  Bhavin                1  98980...
                                                              2  94260...

5 · Worked Examples

Example 1 Easy

Is ENROLL(roll, cid, grade), one grade per cell, in 1NF?

Solution

Yes: every cell is a single atomic value.

Example 2 Medium

A table COURSE(cid, title, prerequisites) stores "C1, C2" in prerequisites for some courses. Give a 1NF design.

Solution

COURSE(cid, title) and PREREQ(cid, prereq_cid) with key (cid, prereq_cid): one prerequisite per row.

Example 3 GATE

"Every relation in BCNF is in 1NF." True or false?

Solution

True. The normal forms are nested: BCNF ⊂ 3NF ⊂ 2NF ⊂ 1NF. Every higher form assumes 1NF.

8 · Connect the Dots

Lesson 4.1.1 showed anomalies; Chapter 4.3 showed how to split safely; this lesson started the normal form ladder with 1NF. Next: 2NF, which forbids non-key facts depending on only part of a composite key.

9 · Self-Test

GATE format. Try every question before opening the vault.

Q1 · MCQ · 1 mark(s) — 1NF

Which table violates 1NF?

1. (A) COURSE(cid, title, credits)
2. (B) STUDENT(roll, name, hobbies) with hobbies = {chess, cricket} in one cell
3. (C) ENROLL(roll, cid, grade)
4. (D) STUDENT(roll, name, cgpa) with one value per cell

Q2 · MCQ · 1 mark(s) — Fix

The preferred fix for a multivalued attribute phone of STUDENT(roll, name, phone) is:

1. (A) deleting the attribute
2. (B) columns phone1, phone2, phone3
3. (C) storing all phones as one comma-separated string
4. (D) a table STUDENT_PHONE(roll, phone) with key (roll, phone)

Q3 · MCQ · 1 mark(s) — Nesting

Which is true?

1. (A) Every relation in 1NF is in BCNF.
2. (B) A relation in 2NF need not be in 1NF.
3. (C) BCNF and 1NF are unrelated.
4. (D) Every relation in 3NF is in 2NF.

Q4 · MSQ · 2 mark(s) — 1NF

Which are 1NF violations?

1. (A) A nested table inside a cell
2. (B) A column holding a list of course codes
3. (C) A NULL in a non-key column
4. (D) Columns course1, course2, course3 (repeating group)

Q5 · MCQ · 2 mark(s) — Expansion

STUDENT(roll, name, phone) is made 1NF by repeating the row for each phone. The new key is:

1. (A) name
2. (B) roll
3. (C) phone
4. (D) (roll, phone)

11 · Concept Ledger

Unlocked in this lesson. From here on, these terms may be used.

first normal form (1NF)atomic domainrepeating groupnormal form ladder