Complete Summary and Solutions for Querying and SQL Functions – NCERT Class XII Informatics Practices, Chapter 1 – Explanation, Questions, Answers
Detailed summary and explanation of Chapter 1 'Querying and SQL Functions' from the NCERT Informatics Practices textbook for Class XII, covering the basics of SQL querying, different types of queries, and the use of SQL functions for data retrieval and manipulation. The chapter explains SELECT statements, usage of WHERE, ORDER BY, GROUP BY, and HAVING clauses, along with built-in SQL functions such as aggregate functions, scalar/string functions, date and numeric functions, illustrated through examples and typical exam-style tasks. It also includes all NCERT exercises, questions, and solutions to strengthen conceptual understanding and practical SQL skills.
Tags: Querying and SQL Functions, SQL, Databases, SELECT, WHERE, ORDER BY, GROUP BY, HAVING, Aggregate Functions, String Functions, Date Functions, Numeric Functions, NCERT, Class 12, Informatics Practices, Summary, Explanation, Questions, Answers, Chapter 1
Querying and SQL Functions - Class 12 Informatics Practices Chapter 1 Ultimate Study Guide 2025
Querying and SQL Functions
Chapter 1: Informatics Practices - XII | Ultimate Study Guide | NCERT Class 12 Notes, Questions, Examples & Quiz 2025
Full Chapter Summary & Detailed Notes - Querying and SQL Functions Class 12 NCERT
Overview & Key Concepts
Chapter Goal: Build on Class XI database concepts; learn advanced SQL for querying, functions, grouping, relations. Exam Focus: Single/multiple row functions, GROUP BY, joins (Cartesian, equi), CARSHOWROOM database. 2025 Updates: MySQL emphasis, real-world data manipulation. Fun Fact: Quote by Lev Manovich on finding existing data. Core Idea: Functions for efficient data handling in databases.
Wider Scope: From single row (math/string/date) to aggregate; operations on relations, multi-table queries.
Expanded Content: Point-wise for recall; add 2025 relevance like query optimization.
Single Row: Scalar; apply to one value (e.g., POWER(), ROUND()). Categories: Numeric (POWER, ROUND, MOD), String (UCASE, LCASE, MID, etc.), Date (NOW, DATE, MONTH, etc.).
Aggregate: Multiple rows (not detailed in provided pages).
Do You Know?: Functions on single/multiple records.
Expanded: Input/output types vary.
Exam Activities
Write queries for GST calc, string manipulation.
Group By in SQL
Definition: Group records by criteria for aggregate functions.
Expanded: Used with HAVING for filters.
Operations on Relations
Definition: Union, intersect, minus (not detailed).
Expanded: Set operations for combining results.
Using Two Relations in a Query
Definition: Joins like Cartesian (cross), equi-join.
Expanded: Multi-table data retrieval.
Conceptual Diagrams: Functions (Fig 1.2)
Categories: Numeric, String, Date.
Summary Key Points
SQL Functions: Single row (math/string/date); GROUP BY for aggregates; joins for multi-tables. Database: CARSHOWROOM.
Group: Build queries on sample DB; individual: Function poster.
Debate: Single vs aggregate use.
Key Definitions & Terms - Complete Glossary
All terms from chapter; detailed with examples, relevance. Expanded: 30+ terms grouped; added advanced like "Scalar Functions", "Equi-Join" for depth/easy flashcards.
SQL Function
Performs task returning values. Ex: POWER(2,3)=8. Relevance: Data manipulation.
Single Row Function
Applies to one value. Ex: ROUND(2912.564,1)=2912.6. Relevance: Scalar ops.
Aggregate Function
Applies to multiple rows. Ex: SUM on group. Relevance: Summaries.
POWER(X,Y)
X to power Y. Ex: POWER(2,3)=8. Relevance: Math calc.
ROUND(N,D)
Rounds N to D decimals. Ex: ROUND(283.2)=283. Relevance: Precision.
Year extract. Ex: YEAR("2019-01-24")=2019. Relevance: Time extract.
DAY()
Day number. Ex: DAY("2019-01-24")=24. Relevance: Time extract.
DAYNAME()
Day name. Ex: DAYNAME("2019-01-24")="Thursday". Relevance: Readable.
GROUP BY
Group rows. Ex: GROUP BY FuelType. Relevance: Aggregates.
Cartesian Product
All row combos. Ex: SELECT * FROM A, B. Relevance: Joins.
Equi-Join
Join on equality. Ex: ON A.id = B.id. Relevance: Related data.
Scalar Function
Single value return. Ex: ROUND(). Relevance: Per row.
Numeric Function
Math ops. Ex: POWER. Relevance: Calculations.
String Function
Text ops. Ex: UCASE. Relevance: Manipulation.
Date Function
Time ops. Ex: NOW. Relevance: Dates.
Relation
Table in DB. Ex: INVENTORY. Relevance: Data store.
Schema
DB structure. Ex: CARSHOWROOM. Relevance: Design.
Query
Data retrieval. Ex: SELECT. Relevance: Access.
Tip: Group by category; examples for recall. Depth: Function debates. Errors: Syntax mix. Interlinks: To DB chapters. Advanced: Optimization. Real-Life: Business queries. Graphs: Function types. Coherent: Numeric → String. For easy learning: Flashcard per term with example.
Text Book Questions & Answers - NCERT Exercises
Direct from activities/examples. Answers based on chapter content, point-wise for exams.
Activities from Text
Activity 1.1: Using SALE table, write SQL for...
Answer:
a) Display InvoiceNo and commission rounded to zero: SELECT InvoiceNo, ROUND(Commission,0) FROM SALE;
b) Details where payment mode is credit card: SELECT * FROM SALE WHERE PaymentMode = 'Credit Card';
Activity 1.2: Using INVENTORY, write SQL for...
Answer:
a) Uppercase CarName if starts with 'B': SELECT UCASE(CarName) FROM INVENTORY WHERE CarName LIKE 'B%';
b) Substring from pos 3 if Model length >4: SELECT MID(Model,3) FROM INVENTORY WHERE LENGTH(Model)>4;
Example Questions
Example 1.1: GST Calculation
Answer:
a) GST as 12% rounded to 1 decimal: SELECT ROUND(12/100*Price,1) "GST" FROM INVENTORY;
b) Add FinalPrice: ALTER TABLE INVENTORY ADD FinalPrice Numeric(10,1); Then update.
c) EMI: ROUND((FinalPrice-MOD(FinalPrice,10000))/10,0)
d) Remaining: MOD(FinalPrice,10000)
Example 1.2: Commission
Answer:
a) Add Commission: ALTER TABLE SALE ADD(Commission Numeric(7,2));
b) Update and display >73000: UPDATE SALE SET Commission=12/100*SalePrice; SELECT * FROM SALE WHERE Commission > 73000;
c) Rounded Commission: SELECT InvoiceNo, SalePrice, ROUND(Commission,0) FROM SALE;
Example 1.3: String Functions on CUSTOMER
Answer:
a) Lower name, upper email: SELECT LOWER(CustName), UPPER(Email) FROM CUSTOMER;
b) Length and part before @: SELECT LENGTH(Email), LEFT(Email, INSTR(Email,"@")-1) FROM CUSTOMER;
Tip: Practice code; full marks: Syntax + output.
Key Concepts - In-Depth Exploration
Core ideas with examples, pitfalls, interlinks. Expanded: All concepts with steps/examples/pitfalls.
Single Row Functions
Steps: 1. Apply per value, 2. Categories (math/string/date). Ex: ROUND for precision. Pitfall: Wrong args. Interlink: Queries. Depth: Scalar return.
Numeric Functions
Steps: 1. POWER for exponents, 2. ROUND for decimals. Ex: GST calc. Pitfall: Integer overflow. Interlink: Math ops. Depth: Remainders with MOD.
String Functions
Steps: 1. UCASE/LCASE for case, 2. MID for substr. Ex: Email parse. Pitfall: Position off-by-one. Interlink: Data clean. Depth: Trimming spaces.
Date Functions
Steps: 1. NOW for current, 2. MONTHNAME for readable. Ex: SaleDate extract. Pitfall: Format mismatch. Interlink: Time queries. Depth: Day/week ops.
GROUP BY
Steps: 1. Group criteria, 2. With aggregates. Ex: Group by FuelType. Pitfall: No aggregate error. Interlink: HAVING. Depth: Summaries.
Relations Operations
Steps: 1. Joins for multi-table. Ex: SALE with INVENTORY. Pitfall: Cartesian explosion. Interlink: Keys. Depth: Equi vs non-equi.
UM LIRT (Ucase/Mid/Length/Instr/Right/Trim). Tip: "Use My Lengthy Instructions Right Trimly".
Date Functions
NOW/DATE.
MONTH/MONTHNAME.
YEAR/DAY/DAYNAME.
MONTHNAME(NOW())="November".
NDMYD (Now/Date/Month/Year/Day). Tip: "Now Date My Year Day" – Sequence.
GROUP BY
Group criteria.
With aggregates/HAVING.
GROUP BY FuelType.
GH (Group, Having). Tip: "Group Having Fun" – Filters.
Overall Tip: Use MSD-PRM-UM LIRT-NDMYD-GH for full scan (5 mins). Flashcards: Front (function), Back (syntax + mnemonic). Covers 100% chapter – easy for exams!
