NEB Class 12 • Computer Science • DBMS • Concept Guide

DDL, DML & Database Models: NEB Class 12 Computer Guide

Master DDL, DML and Database Models through clear concepts, representations, a reliable answer method and exam-focused practice.

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Concepts · Worked reasoning · NEB practice

Quick answer: A database model defines how data and relationships are represented. DDL creates or changes schema objects, while DML retrieves and modifies stored rows; constraints preserve valid states.

Core concept

What DDL, DML and Database Models means physically

A database model defines how data and relationships are represented. DDL creates or changes schema objects, while DML retrieves and modifies stored rows; constraints preserve valid states.

DDL examples: CREATE, ALTER, DROP. DML examples: SELECT, INSERT, UPDATE, DELETE. Use primary and foreign keys to express identity and references.

The institutional reference gives the wider physical model; the CDC curriculum determines the NEB boundary.

Worked checkpoint with interpretation

CREATE TABLE Student(id INT PRIMARY KEY,name VARCHAR(80)); defines structure, while INSERT INTO Student VALUES(1,’Asha’); adds a row.

Do not stop at the number. State what the sign, ratio, spacing, frequency or direction means. A common error is Using DELETE when DROP is intended or vice versa, omitting a WHERE clause in an update, confusing a table row with a column, or ignoring referential integrity.

NEB answer method

Model → evidence → equation → check

First identify the system and what the question asks. Label the diagram, apparatus or reaction with SI quantities, then state the principle before selecting an equation. Solve symbolically where possible and check units, limiting cases and chemical or physical meaning.

StageQuestionEvidence
ModelWhat is idealised?Assumption stated
RepresentationWhich diagram fits?Labels or balanced equation
CalculationWhich relation follows?Symbols then SI values
EvaluationDoes it make sense?Unit, sign and trend check

Make the idea concrete in Nepal

Connect the model to a school laboratory, household technology, health, environment, energy or local material. The example should clarify the science rather than merely mention a place. Compare a prediction with an observation and record uncertainty.

Review the NEB Class 12 Computer Science revision roadmap and the complete Computer Science guide. For online or physical tuition, call 9846662070.

Questions students ask about DDL, DML and Database Models

What is the central idea of DDL, DML and Database Models?

A database model defines how data and relationships are represented. DDL creates or changes schema objects, while DML retrieves and modifies stored rows; constraints preserve valid states.

Which equation should I remember?

DDL examples: CREATE, ALTER, DROP. DML examples: SELECT, INSERT, UPDATE, DELETE. Use primary and foreign keys to express identity and references.

How should I begin a numerical?

Draw the situation, list known quantities in SI units, choose the governing relation symbolically, substitute once and finish with a unit and reasonableness check.

What is a common exam mistake?

Using DELETE when DROP is intended or vice versa, omitting a WHERE clause in an update, confusing a table row with a column, or ignoring referential integrity.

How can I practise this topic?

Alternate one concept explanation, one diagram and two numericals. Revisit errors after a day instead of only rereading the solution.

Where can I get tuition support?

For online or physical KTM Tuition classes, call 9846662070. After Grade 12, the MKS Education panel below gives preparation and pre-counselling contacts.

Frequently asked questions

References and next steps

Scope checked against CDC Nepal; concept support from an institutional reference and OpenStax Science. Continue with the DDL, DML and Database Models cluster.

NEB +2 tuition support

Ask about online or physical tuition

For focused Class 11 and Class 12 subject tuition, lesson clarification, worked-example practice and exam preparation, call 9846662070. Class mode, timetable, teacher availability and fees should be confirmed directly before enrolment.

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