DBMS Topics
HubUnit 1 — Introduction to DBMS & Entity-Relationship ModelAdvantages and Disadvantages of DBMSAggregationCharacteristics of DBMSData IndependenceData ModelsDatabase Users and AdministratorsDBMS LanguagesER DiagramsEntity-Relationship ER ModelIntroduction to DBMSKeys in DBMSRelationships and CardinalitySchema and InstanceSpecialization and GeneralizationUnit 1 Summary — Introduction to DBMS & ER ModelThree-Level Architecture ANSI/SPARC ArchitectureWeak Entity SetUnit 2 — Relational Model & SQLConstraints in SQLCursorsDCL and TCL CommandsDDL CommandsDML CommandsDomain Relational Calculus DRCFunctions and Stored ProceduresJoins in SQLNested Queries SubqueriesRelational AlgebraRelational CalculusRelational ModelSQL IntroductionUnit 2 Summary — Relational Model & SQLTriggers in SQLTuple Relational Calculus TRCViews in SQLArmstrong's Axioms & Closure of AttributesBoyce-Codd Normal Form BCNFClosure of AttributesDependency PreservationFifth Normal Form 5NFFirst Normal Form 1NFFourth Normal Form 4NFFunctional DependencyLossless DecompositionMultivalued DependencyNormal Forms — OverviewNormalization — IntroductionSecond Normal Form 2NFUnit 3 Summary — NormalizationThird Normal Form 3NFUnit 4 — Transaction Management & Concurrency ControlACID PropertiesCheckpointsConcurrency Control & SerializabilityDeadlock in DBMSLock-Based Protocols & Two-Phase LockingLog-Based RecoveryRecovery SystemSerializabilityShadow PagingUnit 4 Summary — Transaction Management & Concurrency ControlTimestamp-Based ProtocolTransaction ManagementTransaction StatesTwo-Phase Locking 2PLUnit 5 — Storage & IndexingB+ TreeB-TreeCost EstimationDynamic HashingFile OrganizationHashing TechniquesIndexing — IntroductionMulti-Level IndexingQuery OptimizationQuery ProcessingSingle-Level IndexingStatic HashingUnit 5 Summary — Storage & IndexingUnit 6 — Advanced Topics in DBMSBig Data and DBMSCloud DatabaseData MiningData WarehouseDatabase SecurityDistributed DatabaseDistributed Query ProcessingDistributed DBMS Architecture, Fragmentation & ReplicationMongoDB — IntroductionNoSQL DatabaseReplication in Distributed DatabasesUnit 6 Summary — Advanced Topics in DBMSViva Voce — DBMSImportant Viva Questions — DBMSInterview Questions — DBMSViva Answers — DBMSDBMS Multiple Choice Questions MCQsDBMS Lab Programs
First Normal Form 1NF
Last Updated : 21 May, 2026
A relation is in First Normal Form 1NF if:
Unit 3116 words7 headingsTables includedExamples included
Definition
A relation is in First Normal Form (1NF) if:
- Every attribute contains atomic (indivisible) values
- Each column contains values of a single type
- Each row is uniquely identifiable (has a primary key)
- There are no repeating groups or arrays
What is an Atomic Value?
An atomic value cannot be broken down further into meaningful components within the context of the database.
| Non-Atomic: "Alice Johnson" | can be split into FirstName, LastName |
| Non-Atomic: "CS101, CS102" | multiple values in one cell |
| Non-Atomic: {Phone1, Phone2, Phone3} | repeating group |
| Atomic: "Alice" | single first name value |
| Atomic: "CS101" | single course ID |
| Atomic: 9812345678 | single phone number |
Violations and Fixes
Violation 1 — Multi-valued Attribute
| SID | Name | PhoneNumbers |
|---|---|---|
| 1001 | Alice | 9811111111,9822222222 |
NOT in 1NF
Violation 2 — Repeating Column Groups
| EmpID | Name | Skill1 | Skill2 | Skill3 |
|---|---|---|---|---|
| 101 | Alice | Java | SQL | Python |
NOT in 1NF
Fix
Violation 3 — Composite Value in One Column
| EmpID | FullAddress |
|---|---|
| 101 | 12 MG Rd, Delhi |
NOT in 1NF
Fix
After Applying 1NF
| Student | Courses |
|---|---|
| Alice | CS101, MATH201, PHY301 |
| Bob | CS101, MATH201 |
| Carol | PHY301 |
Students can enroll in many courses, and each course can have many students.
Note: After 1NF, the table may have partial dependencies (SName depends only on SID) — these are fixed in 2NF.
Exam Focus
Revise definitions, diagrams, examples, and short-answer points for First Normal Form 1NF.
Interview Use
Prepare one clear explanation, one practical example, and one common mistake for this DBMS topic.
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Unit 3Fifth Normal Form 5NFA relation R is in Fifth Normal Form 5NF — also called Project-Join Normal Form PJ/NF — if, for every non-trivial join dependency R1, R2, ..., Rn in R:Unit 3Fourth Normal Form 4NFA relation R is in Fourth Normal Form 4NF if, for every non-trivial multivalued dependency X →→ Y in R:Unit 3Second Normal Form 2NFA relation is in Second Normal Form 2NF if:Unit 3Third Normal Form 3NFA relation is in Third Normal Form 3NF if:Unit 3Normal Forms — OverviewUnit 3Boyce-Codd Normal Form BCNFA relation R is in BCNF Boyce-Codd Normal Form if, for every non-trivial functional dependency X → Y in R: