10+Times Asked
~50Total Marks
5Topics
MediumPriority
1 RDBMS and GIS
- RDBMS: Data stored in tables (relations) with rows (tuples) and columns (attributes).
- Tables linked via primary keys (unique identifier) and foreign keys (reference to another table).
- GIS uses RDBMS to store attribute data linked to spatial features by a common ID field.
2 Types of DBMS
- Hierarchical: Tree structure (parent-child). Fast but rigid. Example: IMS.
- Network: Graph structure (many-to-many). Flexible but complex. Example: CODASYL.
- Relational: Tables with keys. Most common. Example: PostgreSQL, Oracle, SQL Server.
- Object-oriented: Stores complex objects with methods. Example: ObjectStore.
- Object-relational: Combines relational + object features. Example: PostGIS (spatial extension of PostgreSQL).
3 Normalisation
- 1NF: Each cell contains a single atomic value. No repeating groups.
- 2NF: 1NF + no partial dependency (every non-key attribute depends on the entire primary key).
- 3NF: 2NF + no transitive dependency (non-key attributes depend only on the primary key, not on other non-key attributes).
Purpose of normalisation: Reduce redundancy, prevent update anomalies, ensure data integrity. Over-normalisation can hurt performance — balance with denormalisation for query speed.
4 SQL and JOIN Operations
- SQL (Structured Query Language): SELECT, INSERT, UPDATE, DELETE, CREATE, ALTER, DROP.
- INNER JOIN: Returns rows with matching values in both tables.
- LEFT JOIN: All rows from left table + matching from right.
- Spatial SQL (PostGIS): ST_Intersects, ST_Buffer, ST_Contains, ST_Distance.
5 Database Querying in GIS
- Attribute query: "Select all parcels WHERE area > 500 m²"
- Spatial query: "Select all schools WITHIN 1 km of a hospital."
- Combined: "Select commercial buildings WITHIN flood zone AND value > 10 million."
Past Exam Questions
+What is RDBMS? How is it used in GIS? (2073, 2076, 2079)
Tables with rows/columns. Primary/foreign keys. GIS links spatial features to attribute tables via ID field. Supports SQL queries.
+Explain types of DBMS. (2072, 2075)
Hierarchical, Network, Relational, Object-oriented, Object-relational. Give structure and example for each. Relational most common in GIS.
+Explain normalisation with 1NF, 2NF, 3NF examples. (2074, 2078, 2081)
Define each normal form. Show a table violating each form and its corrected version. Explain partial vs transitive dependency.
+What are SQL JOIN operations? Write example queries. (2076, 2080)
INNER JOIN, LEFT JOIN. Write: SELECT parcels.id, owners.name FROM parcels INNER JOIN owners ON parcels.owner_id = owners.id WHERE parcels.area > 500;
+Differentiate attribute query and spatial query with examples. (2071, 2074, 2082)
Attribute: condition on column values. Spatial: condition on location/geometry. Combined: both at once. Give one GIS example for each type.