Write the output produced by the following SQL commands: (a) SELECT POW(2,3); (b) SELECT ROUND(123.2345, 2), ROUND(342.9234, -1); (c) SELECT LENGTH("Informatics Practices"); (d) SELECT YEAR("1979/11/26"), MONTH("1979/11/26"), DAY("1979/11/26"), MONTHNAME("1979/11/26"); (e) SELECT LEFT("INDIA", 3), RIGHT("Computer Science", 4); (f) SELECT MID("Informatics", 3, 4), SUBSTR("Practices", 3);

Write the output produced by the following SQL commands: (a) SELECT POW(2,3); (b) SELECT ROUND(123.2345, 2), R

Exercises · Q2

Q. Write the output produced by the following SQL commands:

(a) SELECT POW(2,3);

(b) SELECT ROUND(123.2345, 2), ROUND(342.9234, -1);

(d) SELECT YEAR("1979/11/26"), MONTH("1979/11/26"), DAY("1979/11/26"), MONTHNAME("1979/11/26");

(e) SELECT LEFT("INDIA", 3), RIGHT("Computer Science", 4);

(f) SELECT MID("Informatics", 3, 4), SUBSTR("Practices", 3);

Tamil Nadu DgeTextbookSubjective· 4mImportance★★★★★

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Concept understanding — String Functions

String Functions: A First Look

Think of a string as a piece of text — a word, a sentence, a name, or even a single character. In computing, strings are everywhere: your name in a form, a product code in a database, a tweet, a paragraph in a document. String functions are the tools that let you work with that text: cut it, join it, clean it, search inside it, or change its appearance.

You already use these ideas in everyday life. When you take a long sentence and pick out just the first word, you are performing a "substring" operation. When you combine your first name and last name into a full name, you are "concatenating" two strings. When you check whether an email address contains an "@" symbol, you are "searching" within a string. String functions are just these familiar actions, given precise names and made available in software.

The Core Idea

A string function takes one or more strings as input and returns a new string or a piece of information about the string. The function does not change the original string — it produces a result based on it. This is important: the original data stays untouched unless you explicitly replace it.

Note

Strings are treated as sequences of characters. Each character — letter, digit, space, punctuation — occupies a position. In most systems, counting starts at 1 (the first character is position 1), though some languages start at 0. Always check which convention your tool uses.

Common Types of String Functions

1. Changing Case

These functions convert text to uppercase or lowercase. They are useful when you want to compare names or addresses without worrying about whether someone typed "Delhi" or "delhi".

UPPER or UCASE: converts all letters to capitals
LOWER or LCASE: converts all letters to small letters
PROPER or TITLE: capitalises the first letter of each word

2. Extracting Parts of a String

You often need to pull out a specific portion of text — the first name from a full name, the area code from a phone number, the year from a date.

LEFT: returns a given number of characters from the start
RIGHT: returns a given number of characters from the end
MID or SUBSTRING: returns characters starting from a specified position for a specified length

3. Finding and Replacing

These functions let you search inside text and optionally replace what you find.

FIND or INSTR: locates the position of one string inside another
REPLACE: substitutes all occurrences of a substring with another string
TRIM: removes extra spaces from the beginning and end of a string

4. Joining and Splitting

CONCAT or the ampersand (&): joins two or more strings end to end
SPLIT (in some systems): breaks a string into parts based on a delimiter (like a comma or space)

5. Measuring Length

LEN or LENGTH: returns the number of characters in a string

Why They Matter

In any real-world data task — whether you are cleaning a customer list, generating reports, validating user input, or preparing data for analysis — you will work with text. String functions give you the power to:

Standardise messy data (e.g., "john", "John", "JOHN" all become "John")
Extract meaningful pieces from longer text (e.g., get the domain from an email)
Combine information from different columns (e.g., first name + last name)
Check for errors or patterns (e.g., does a product code have exactly 10 characters?)
Remove unwanted characters or spaces

Important

String functions are case-sensitive by default in many systems. "Apple" and "apple" are different strings unless you explicitly convert them to the same case before comparing. This is a common source of bugs — always decide whether case matters for your task.

A Simple Example in Plain Language

Suppose you have a list of full names like "Ms. Priya Sharma". You want to extract just the last name. You would:

Find the position of the space after "Ms." — that is position 4
Find the position of the space after "Priya" — that is position 11
Use a substring function to extract characters from position 5 to position 10 (the first name)
Use a substring function to extract characters from position 12 onward (the last name)

Each of these steps uses a string function. The computer does not "understand" names — it just follows the rules you give it using these tools.

The Big Picture

String functions are not about memorising a list of names. They are about recognising that text is data, and data needs manipulation. Every time you need to clean, combine, search, or reshape text, you are reaching for a string function. Learn the logic — what each type does — and the specific names will follow naturally when you encounter them in a particular software or programming language.

Shape of question

This is a code / query task asking for the output of six SQL commands that use built-in functions (numeric, string, and date).

(a) `SELECT POW(2,3);`

SELECT POW(2,3);

POW(base, exponent) raises the base to the power of the exponent. Here $2^3 = 8$ .

Output:

POW(2,3)
8

(b) `SELECT ROUND(123.2345, 2), ROUND(342.9234, -1);`

SELECT ROUND(123.2345, 2), ROUND(342.9234, -1);

ROUND(number, decimals) rounds to the specified number of decimal places. A positive second argument rounds to that many places after the decimal; a negative argument rounds to the left of the decimal point.

ROUND(123.2345, 2) → $123.23$ (two decimal places)
ROUND(342.9234, -1) → $340$ (rounds to the nearest ten)

Output:

ROUND(123.2345, 2)	ROUND(342.9234, -1)
123.23	340

(c) `SELECT LENGTH("Informatics Practices");`

SELECT LENGTH("Informatics Practices");

LENGTH(string) returns the number of characters in the string, including spaces. "Informatics Practices" has 21 characters (11 in "Informatics", 1 space, 9 in "Practices").

Output:

LENGTH("Informatics Practices")
21

(d) `SELECT YEAR("1979/11/26"), MONTH("1979/11/26"), DAY("1979/11/26"), MONTHNAME("1979/11/26");`

SELECT YEAR("1979/11/26"), MONTH("1979/11/26"), DAY("1979/11/26"), MONTHNAME("1979/11/26");

These date functions extract components from the date string "1979/11/26" (26 November 1979):

YEAR() → 1979
MONTH() → 11
DAY() → 26
MONTHNAME() → "November"

Output:

YEAR("1979/11/26")	MONTH("1979/11/26")	DAY("1979/11/26")	MONTHNAME("1979/11/26")
1979	11	26	November

(e) `SELECT LEFT("INDIA", 3), RIGHT("Computer Science", 4);`

SELECT LEFT("INDIA", 3), RIGHT("Computer Science", 4);

LEFT(string, n) extracts the leftmost $n$ characters: "INDIA" → "IND"
RIGHT(string, n) extracts the rightmost $n$ characters: "Computer Science" → "ence"

Output:

LEFT("INDIA", 3)	RIGHT("Computer Science", 4)
IND	ence

(f) `SELECT MID("Informatics", 3, 4), SUBSTR("Practices", 3);`

SELECT MID("Informatics", 3, 4), SUBSTR("Practices", 3);

MID(string, start, length) extracts a substring starting at position start (1-indexed) for length characters. From "Informatics", starting at position 3 ('f') for 4 characters → "form"
SUBSTR(string, start) extracts from position start to the end. From "Practices", starting at position 3 ('a') → "actices"

Output:

MID("Informatics", 3, 4)	SUBSTR("Practices", 3)
form	actices

✓Final answer

The six queries produce: (a) 8; (b) 123.23 and 340; (c) 21; (d) 1979, 11, 26, November; (e) "IND" and "ence"; (f) "form" and "actices".

Predicting the output of SQL built-in functions for numeric operations, string manipulation, and date extraction.

Why these functions matter

SQL provides a rich library of built-in functions that transform data directly in queries. Numeric functions like POW and ROUND handle mathematical operations; string functions like LENGTH, LEFT, RIGHT, MID, and SUBSTR slice and measure text; date functions like YEAR, MONTH, DAY, and MONTHNAME extract components from dates. Understanding their exact behavior—return types, indexing conventions, rounding rules—is essential for writing correct queries and predicting results.

Each function below is deterministic: given the same input, it always returns the same output. The key is knowing the signature and the edge cases.

(a) SELECT POW(2,3);

POW(base, exponent) raises the base to the power of the exponent: $2^3 = 8$ .

SELECT POW(2,3);

Output:

POW(2,3)
8

(b) SELECT ROUND(123.2345, 2), ROUND(342.9234, -1);

ROUND(number, decimals) rounds a number to the specified number of decimal places. When decimals is negative, it rounds to the left of the decimal point.

ROUND(123.2345, 2): round to 2 decimal places → $123.23$ (the third decimal is 4, which is < 5, so we round down).
ROUND(342.9234, -1): round to the nearest ten (one place left of the decimal) → $340$ (the units digit is 2, which is < 5, so the tens place stays 4, giving 340).

SELECT ROUND(123.2345, 2), ROUND(342.9234, -1);

Output:

ROUND(123.2345, 2)	ROUND(342.9234, -1)
123.23	340

(c) SELECT LENGTH("Informatics Practices");

LENGTH(string) returns the number of characters in the string, including spaces.

"Informatics Practices" has:

"Informatics" = 11 characters
" " (space) = 1 character
"Practices" = 9 characters
Total = $11 + 1 + 9 = 21$

SELECT LENGTH("Informatics Practices");

Output:

LENGTH("Informatics Practices")
21

(d) SELECT YEAR("1979/11/26"), MONTH("1979/11/26"), DAY("1979/11/26"), MONTHNAME("1979/11/26");

These functions extract components from a date string in the format YYYY/MM/DD:

YEAR("1979/11/26") → 1979
MONTH("1979/11/26") → 11
DAY("1979/11/26") → 26
MONTHNAME("1979/11/26") → "November" (the name of the 11th month)

SELECT YEAR("1979/11/26"), MONTH("1979/11/26"), DAY("1979/11/26"), MONTHNAME("1979/11/26");

Output:

YEAR("1979/11/26")	MONTH("1979/11/26")	DAY("1979/11/26")	MONTHNAME("1979/11/26")
1979	11	26	November

(e) SELECT LEFT("INDIA", 3), RIGHT("Computer Science", 4);

LEFT(string, n) returns the leftmost n characters.
- LEFT("INDIA", 3) → "IND"
RIGHT(string, n) returns the rightmost n characters.
- RIGHT("Computer Science", 4) → "ence" (the last 4 characters of "Computer Science")

SELECT LEFT("INDIA", 3), RIGHT("Computer Science", 4);

Output:

LEFT("INDIA", 3)	RIGHT("Computer Science", 4)
IND	ence

(f) SELECT MID("Informatics", 3, 4), SUBSTR("Practices", 3);

MID(string, start, length) extracts length characters starting from position start. In MySQL, string positions are 1-indexed.
- MID("Informatics", 3, 4): start at position 3 (the letter 'f'), take 4 characters → "form"
  - Positions: I(1), n(2), f(3), o(4), r(5), m(6), a(7), t(8), i(9), c(10), s(11)
  - Characters 3–6: "form"
SUBSTR(string, start) (or SUBSTRING) extracts from position start to the end of the string.
- SUBSTR("Practices", 3): start at position 3 (the letter 'a'), take the rest → "actices"
  - Positions: P(1), r(2), a(3), c(4), t(5), i(6), c(7), e(8), s(9)
  - From position 3 onward: "actices"

SELECT MID("Informatics", 3, 4), SUBSTR("Practices", 3);

Output:

MID("Informatics", 3, 4)	SUBSTR("Practices", 3)
form	actices

Watch out

SQL string functions are 1-indexed, not 0-indexed like Python. MID("Informatics", 1, 1) returns "I", not "n".

✓Final answer

(a) 8 (b) 123.23, 340 (c) 21 (d) 1979, 11, 26, November (e) IND, ence (f) form, actices

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Q.Write the output produced by the following SQL commands:

Why these functions matter

(a) SELECT POW(2,3);

(b) SELECT ROUND(123.2345, 2), ROUND(342.9234, -1);

(c) SELECT LENGTH("Informatics Practices");

(d) SELECT YEAR("1979/11/26"), MONTH("1979/11/26"), DAY("1979/11/26"), MONTHNAME("1979/11/26");

(e) SELECT LEFT("INDIA", 3), RIGHT("Computer Science", 4);

(f) SELECT MID("Informatics", 3, 4), SUBSTR("Practices", 3);

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