Answer the following questions: (a) Define RDBMS. Name any two RDBMS software. (b) What is the purpose of the

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Q. Answer the following questions:

(a) Define RDBMS. Name any two RDBMS software.

(b) What is the purpose of the following clauses in a SELECT statement?

(i) ORDER BY

(ii) HAVING

(d) What do you understand by Cartesian Product?

(e) Write the name of the functions to perform the following operations:

(i) To display the day like "Monday", "Tuesday", from the date when India got independence.

(ii) To display the specified number of characters from a particular position of a given string.

(iii) To display the name of the month in which you were born.

(iv) To display your name in capital letters.

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Concept understanding — SQL Query Concepts

SQL Query Concepts — A First Look

Think of a library. You walk in, and instead of wandering through endless shelves, you go to the librarian and say: "Give me all the books by Tagore published after 1950, sorted by title." The librarian knows exactly where everything is, finds what you asked for, and hands you the list. That's what SQL does — but for data stored in a computer.

SQL stands for Structured Query Language. It is the language we use to talk to databases. A database is just a collection of related information stored in tables — like an Excel workbook with multiple sheets, but far more powerful and organised.

The core idea: tables and queries

A database stores data in tables. Each table has rows (records) and columns (fields). For example, a Students table might have columns like RollNo, Name, City, and Marks. Each row is one student's complete information.

A query is simply a question you ask the database. You write it in SQL, and the database returns an answer — usually a new table made from the data that matches your question.

Note

SQL is not a programming language like Python or Java. You don't tell the computer how to find the data. You only say what data you want. The database figures out the fastest way to get it.

The most common SQL command: SELECT

Almost every query begins with SELECT. It means "show me this data." The basic structure is:

SELECT column1, column2 FROM table_name WHERE condition;

Read it like a sentence: "Select these columns from this table where this condition is true."

If you want all columns, you write SELECT *. The asterisk is a shortcut meaning "everything."

Filtering with WHERE

The WHERE clause is your filter. It keeps only the rows that satisfy a condition. For example, if you want students from Delhi only, you write:

SELECT * FROM Students WHERE City = 'Delhi';

You can combine conditions using AND (both must be true) and OR (at least one must be true). This is exactly like everyday logic: "Show me students from Delhi AND who scored above 80."

Sorting with ORDER BY

Data often comes back in no particular order. To arrange it, use ORDER BY. You can sort ascending (smallest first, which is the default) or descending (largest first) using DESC.

SELECT Name, Marks FROM Students ORDER BY Marks DESC;

This gives you a ranked list — highest marks first.

Why SQL matters for commerce and humanities

You will never calculate a formula in SQL. That is not what it does. What SQL does is organise, filter, and retrieve information — and that is the foundation of every data-driven decision.

A marketing manager uses SQL to find customers who haven't purchased in six months. An HR analyst uses it to list employees eligible for promotion. A historian might use it to query a database of census records from 1901. The skill is not in memorising syntax but in learning to ask the right questions of your data.

Important

SQL is about precision in asking. A small mistake in a condition — writing City = 'delhi' instead of 'Delhi' — can give you zero results even though the data exists. The database does exactly what you tell it, not what you meant.

A few key points to remember

SQL is case-insensitive for keywords (select works the same as SELECT), but data values are often case-sensitive depending on the database.
Text values must be enclosed in single quotes. Numbers are written without quotes.
Every SQL statement ends with a semicolon (;).
You can combine multiple clauses: SELECT ... FROM ... WHERE ... ORDER BY ...

You do not need to memorise every command today. The real learning begins when you start writing queries and seeing what the database returns. Start with simple SELECT statements, add a WHERE condition, then try sorting. Each time, you are asking the database a question — and it answers instantly.

Here are the answers to the questions:

(a) Define RDBMS. Name any two RDBMS software.

A Relational Database Management System (RDBMS) is a software system used to create, manage, and query relational databases. In an RDBMS, data is organized into tables (also known as relations), which consist of rows (records) and columns (attributes). These tables are related to each other through common fields, allowing for efficient storage, retrieval, and manipulation of structured data. RDBMS uses Structured Query Language (SQL) for data definition and manipulation.

Two RDBMS software examples are:

MySQL
Oracle Database

(b) What is the purpose of the following clauses in a SELECT statement?

ORDER BY The ORDER BY clause is used to sort the result set of a SELECT query. It arranges the rows in ascending (ASC) or descending (DESC) order based on the values of one or more specified columns. If no order is specified, ASC (ascending) is the default. This clause is typically placed after the FROM and WHERE clauses in a SELECT statement.
HAVING The HAVING clause is used to filter groups of rows based on a specified condition. Unlike the WHERE clause, which filters individual rows before grouping, HAVING filters the results of aggregate functions (like SUM(), COUNT(), AVG(), MIN(), MAX()) applied to groups created by the GROUP BY clause. It is always used in conjunction with GROUP BY and is placed after it.

(c) Cite any two differences between Single-row functions and Aggregate functions.

Here are two key differences between Single-row functions and Aggregate functions:

Number of Rows Processed and Returned:
- Single-row functions operate on a single row at a time and return a single result for each row processed. If there are 10 rows in the input, a single-row function will produce 10 output values (one for each row).
- Aggregate functions (also known as multi-row functions) operate on a set of rows (a group) and return a single summary result for that entire group. If there are 10 rows in a group, an aggregate function will produce only 1 output value for that group.
Usage with GROUP BY Clause:
- Single-row functions can be used in the SELECT list, WHERE clause, and ORDER BY clause, and do not require the GROUP BY clause.
- Aggregate functions are typically used in the SELECT list in conjunction with the GROUP BY clause to perform calculations on subsets of data. When used without GROUP BY, they treat the entire result set as a single group. They cannot be directly used in the WHERE clause; instead, the HAVING clause is used to filter based on their results.

(d) What do you understand by Cartesian Product?

A Cartesian Product, also known as a Cross Join, is a type of join operation in SQL that combines every row from the first table with every row from the second table. If Table A has $m$ rows and Table B has $n$ rows, their Cartesian Product will result in a new table containing $m \times n$ rows. The number of columns in the resulting table will be the sum of the number of columns in Table A and Table B. This operation is performed when no join condition is specified between two tables, or explicitly using the CROSS JOIN keyword. It typically generates a large and often meaningless result set unless used intentionally for specific purposes, such as generating all possible combinations.

(e) Write the name of the functions to perform the following operations:

To display the day like "Monday", "Tuesday", from the date when India got independence. DAYNAME()
To display the specified number of characters from a particular position of a given string. SUBSTRING() (or MID())
To display the name of the month in which you were born. MONTHNAME()
To display your name in capital letters. UPPER() (or UCASE())
✓Final answer
$The answer defines RDBMS and names two software, explains the purpose of ORDER BY and HAVING clauses, cites two differences between single-row and aggregate functions, explains Cartesian Product, and provides the SQL functions DAYNAME(), SUBSTRING(), MONTHNAME(), and UPPER() for the specified operations.$

This solution defines RDBMS, explains the purpose of ORDER BY and HAVING clauses, differentiates between single-row and aggregate functions, clarifies the Cartesian Product, and identifies specific SQL functions for date and string manipulation.

(a) Define RDBMS. Name any two RDBMS software.

A Relational Database Management System (RDBMS) is a software system used to create, manage, and query relational databases. In an RDBMS, data is organized into tables, also known as relations, which consist of rows (records or tuples) and columns (attributes or fields). These tables are related to each other through common columns, typically using primary and foreign keys, which helps maintain data integrity and allows for efficient data retrieval and manipulation. RDBMS uses Structured Query Language (SQL) for managing and querying data.

Two common RDBMS software are:

MySQL
Oracle Database (Other examples include PostgreSQL, Microsoft SQL Server, SQLite)

(b) What is the purpose of the following clauses in a SELECT statement?

The SELECT statement is used to retrieve data from a database. Various clauses can be added to a SELECT statement to filter, group, and order the results.

(i) ORDER BY

The ORDER BY clause is used to sort the result set of a SELECT query. It arranges the rows in ascending (ASC) or descending (DESC) order based on the values in one or more specified columns. If no order is specified, ASC (ascending) is the default. This clause is typically placed after the FROM, WHERE, and GROUP BY clauses in a SELECT statement.

Example:

To sort employees by their salary in descending order:

SELECT EmpName, Salary
FROM Employees
ORDER BY Salary DESC;

(ii) HAVING

The HAVING clause is used to filter groups of rows based on a specified condition. Unlike the WHERE clause, which filters individual rows before they are grouped, the HAVING clause filters groups after they have been formed by the GROUP BY clause and after aggregate functions have been applied. It is used with aggregate functions (like SUM(), COUNT(), AVG(), MAX(), MIN()) to apply conditions to the results of these aggregations.

Example:

To display departments where the average salary is greater than 50000:

SELECT Department, AVG(Salary)
FROM Employees
GROUP BY Department
HAVING AVG(Salary) > 50000;

Important

The key difference between WHERE and HAVING is that WHERE filters individual rows before grouping, while HAVING filters groups after grouping and aggregation.

(c) Cite any two differences between Single-row functions and Aggregate functions.

SQL functions can be broadly categorized into single-row (or scalar) functions and aggregate (or group) functions.

Here are two key differences:

Feature	Single-row Functions	Aggregate Functions
Input & Output	Take one row as input and return one value per row.	Take a set of rows (a group) as input and return a single value for the entire group.
Usage with GROUP BY	Can be used in `SELECT`, `WHERE`, `ORDER BY` clauses, and do not require a `GROUP BY` clause.	Typically used with the `GROUP BY` clause to perform calculations on groups of rows. If `GROUP BY` is omitted, they operate on the entire result set as a single group.
Examples	`UPPER()`, `LOWER()`, `LENGTH()`, `SUBSTRING()`, `DAYNAME()`, `MONTHNAME()`, `NOW()`, `MOD()`	`SUM()`, `COUNT()`, `AVG()`, `MAX()`, `MIN()`

(d) What do you understand by Cartesian Product?

The Cartesian Product, also known as a cross join, is a relational algebra operation that combines every row from one table with every row from another table. If Table A has m rows and Table B has n rows, their Cartesian Product will result in a new table containing m * n rows. The number of columns in the resulting table will be the sum of the number of columns in Table A and Table B.

In SQL, a Cartesian Product occurs when you join two or more tables without specifying any join condition (i.e., without an ON clause for JOIN or a WHERE clause for implicit joins).

Example:

If TableA has 3 rows and TableB has 2 rows, their Cartesian Product will have $3 \times 2 = 6$ rows.

SELECT *
FROM TableA, TableB;

SELECT *
FROM TableA CROSS JOIN TableB;

Watch out

A Cartesian Product often produces a very large and usually meaningless result set if it's not the intended operation. It's a common mistake when forgetting to specify a join condition between tables.

(e) Write the name of the functions to perform the following operations:

Assuming standard SQL functions commonly found in RDBMS like MySQL:

(i) To display the day like "Monday", "Tuesday", from the date when India got independence.

Function Name: DAYNAME()
Explanation: This function takes a date as input and returns the full name of the weekday (e.g., 'Monday', 'Tuesday').
Example Usage: DAYNAME('1947-08-15') would return 'Friday'.

(ii) To display the specified number of characters from a particular position of a given string.

Function Name: SUBSTRING() (or SUBSTR())
Explanation: This function extracts a substring of a specified length from a string, starting at a particular position.
Example Usage: SUBSTRING('Hello World', 7, 5) would return 'World'.

(iii) To display the name of the month in which you were born.

Function Name: MONTHNAME()
Explanation: This function takes a date as input and returns the full name of the month (e.g., 'January', 'February').
Example Usage: If you were born on '2005-03-10', MONTHNAME('2005-03-10') would return 'March'.

(iv) To display your name in capital letters.

Function Name: UPPER() (or UCASE())
Explanation: This function converts all characters in a given string to uppercase.
Example Usage: UPPER('john doe') would return 'JOHN DOE'.

✓Final answer

RDBMS organizes data into related tables; MySQL and Oracle Database are two examples. ORDER BY sorts the result set; HAVING filters groups based on aggregate conditions. Single-row functions return one value per input row, while aggregate functions return one value per group of rows. Cartesian Product combines every row from one table with every row from another. (i) DAYNAME(), (ii) SUBSTRING(), (iii) MONTHNAME(), (iv) UPPER() .

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Q.Answer the following questions:

(a) Define RDBMS. Name any two RDBMS software.

(b) What is the purpose of the following clauses in a SELECT statement?

(i) ORDER BY

(ii) HAVING

(c) Cite any two differences between Single-row functions and Aggregate functions.

(d) What do you understand by Cartesian Product?

(e) Write the name of the functions to perform the following operations:

(i) To display the day like "Monday", "Tuesday", from the date when India got independence.

(ii) To display the specified number of characters from a particular position of a given string.

(iii) To display the name of the month in which you were born.

(iv) To display your name in capital letters.

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