By Piyush Wairale (M.Tech, IIT Madras) · Former Instructor, IIT Madras BS Degree Programme · Mentor to 20,000+ GATE aspirants · Updated November 2026

GATE CSE 2027 Databases Syllabus (Official, IIT Madras)

Section 9 of the CS paper: ER-model. Relational model: relational algebra, tuple calculus, SQL. Integrity constraints, normal forms. File organization, indexing (e.g., B and B+ trees). Transactions and concurrency control.

Full paper structure: GATE CS 2027 syllabus and exam pattern.

Topic-wise Weightage and Priority

ER Model

Entities, attributes (simple, composite, multivalued, derived), relationships and cardinality (1:1, 1:N, M:N), participation (total/partial) and weak entities. Mapping rules for minimum tables: a 1:N relationship merges into the N side; an M:N relationship needs its own table; a multivalued attribute needs its own table; a 1:1 with total participation on one side can merge into that side.

Relational Algebra, Tuple Calculus and SQL

Relational algebra operators: σ (select), π (project, removes duplicates), ×, ⋈ (joins), ∪, −, ρ, and division (for “for all” queries). Tuple relational calculus expresses queries as {t | P(t)}; safe TRC is equivalent in power to relational algebra. In SQL, remember that SELECT keeps duplicates unless DISTINCT is used, WHERE filters rows before GROUP BY and HAVING filters groups after, and NOT IN fails silently if the subquery returns NULL. For a worked, row-by-row walkthrough, see SQL and relational algebra evaluated step by step.

Integrity Constraints, Keys and Normal Forms

Find candidate keys with attribute closure: start with attributes that never appear on the right side of any FD (they must be in every key). A relation with n attributes and a single-attribute candidate key has 2ⁿ⁻¹ superkeys.

A decomposition of R into R1 and R2 is lossless if R1 ∩ R2 is a superkey of R1 or of R2. A 3NF decomposition that is lossless and dependency-preserving always exists; BCNF may lose dependency preservation.

File Organization and Indexing (B and B+ Trees)

Primary, clustering and secondary indexes; dense vs sparse indexes. In a B+ tree, all records (or record pointers) are at the leaves, which are linked for range queries; internal nodes hold only keys and child pointers, so B+ trees have higher fan-out than B trees. Internal node order p satisfies p × (block pointer size) + (p − 1) × (key size) ≤ block size. Search cost = tree height + 1 data block access (for a primary index).

Transactions and Concurrency Control

ACID properties. A schedule is conflict serializable iff its precedence graph (edges for conflicting read-write, write-read, write-write pairs on the same item by different transactions) is acyclic. Every conflict-serializable schedule is view serializable, not conversely (blind writes). Recoverable: a transaction commits only after those it read from commit; cascadeless: reads only committed data; strict: no read or write of uncommitted data. Two-phase locking guarantees conflict serializability but not deadlock freedom; strict 2PL also gives cascadeless schedules. Timestamp ordering and Thomas’ write rule are also in scope.

Five GATE-Style Problems, Solved

Q1 (MCQ). R(A, B, C, D) with A → B, B → C, C → D. Candidate key(s)?
Solution: A never appears on a right side and A⁺ = ABCD, so the only candidate key is A.

Q2 (NAT). How many superkeys does that relation have?
Solution: Any set containing A: 2³ = 8.

Q3 (MCQ). R(A, B, C) with AB → C and C → B. Highest normal form?
Solution: Candidate keys are AB and AC, so all attributes are prime. C → B violates BCNF (C is not a superkey) but satisfies 3NF (B is prime). Answer: 3NF.

Q4 (MCQ). Is the schedule r1(A), w2(A), w1(A) conflict serializable?
Solution: r1(A) before w2(A) gives T1 → T2; w2(A) before w1(A) gives T2 → T1. Cycle, so not conflict serializable.

Q5 (NAT). Block size 1024 B, key 10 B, block pointer 6 B. Maximum order of a B+ tree internal node?
Solution: 6p + 10(p − 1) ≤ 1024 gives 16p ≤ 1034, so p = 64.

Common Mistakes to Avoid

Missing a candidate key: after finding one, check whether swapping in attributes from FD left sides gives another.

Calling a relation not-3NF without checking whether the right-side attribute is prime.

Drawing precedence edges for read-read pairs: only conflicting operations count.

Forgetting that π removes duplicates while SQL SELECT does not.

Using the leaf-node formula for internal-node order in B+ trees.

4-Week Preparation Strategy

Week 1: ER model, relational algebra, TRC and SQL. Week 2: FDs, closures, keys, normal forms and decomposition. Week 3: File organization and B/B+ trees, then transactions and concurrency control. Week 4: 10 years of GATE CS DBMS questions and the DBMS tests in the GATE CSE 2027 Test Series.

FAQs: GATE CSE 2027 DBMS

GATE CSE 2027: All Subject-wise Guides

1. Engineering Mathematics · 2. Digital Logic · 3. Computer Organization & Architecture · 4. Programming & Data Structures · 5. Algorithms · 6. Theory of Computation · 7. Compiler Design · 8. Operating System · 9. Databases (DBMS) · 10. Computer Networks

Full paper overview: GATE CS 2027 Syllabus, Exam Pattern & Cutoff. Practise all ten subjects in one place with the GATE CSE 2027 Test Series.