String Functions in SQL

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Now STRING FUNCTIONS in SQL in the same crystal-clear pattern:

• One base table

• Question

• SQL

• Exact OUTPUT shown

• ✔ short explanation

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📘 Base Tables (Used for ALL Examples)

employees

emp_id	first_name	last_name
1	Amit	Kumar
2	Neha	Singh
3	Ravi	Verma

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products

product_id	product_name
1	Laptop
2	MobilePhone
3	Headphones

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customers

customer_id	full_name
1	Amit Kumar␠
2	Neha Singh␠

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orders

order_id	order_number
1	ORD2024001
2	ORD2024123

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product_descriptions

id	description
1	old_string model
2	new old_string version

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🧾 Summary Table (Questions)

No.	Function	Question
1	CONCAT	Join first & last name
2	SUBSTRING	Extract part of string
3	CHAR_LENGTH	Find string length
4	UPPER	Convert to uppercase
5	LOWER	Convert to lowercase
6	TRIM	Remove extra spaces
7	LEFT	Get left characters
8	RIGHT	Get right characters
9	REPLACE	Replace text

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1️⃣ CONCAT()

Question: Show full name of employees.

SELECT CONCAT(first_name, ' ', last_name) AS full_name
FROM employees;

✅ Output

full_name
Amit Kumar
Neha Singh
Ravi Verma

✔ Joins multiple strings into one

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2️⃣ SUBSTRING() / SUBSTR()

Question: Extract first 5 characters of product name.

SELECT SUBSTRING(product_name FROM 1 FOR 5) AS substring
FROM products;

✅ Output

substring
Lapto
Mobil
Headp

✔ Extracts part of a string

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3️⃣ CHAR_LENGTH() / LENGTH()

Question: Find length of each product name.

SELECT product_name, CHAR_LENGTH(product_name) AS length
FROM products;

✅ Output

product_name	length
Laptop	6
MobilePhone	11
Headphones	10

✔ Counts number of characters

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4️⃣ UPPER()

Question: Convert employee first names to uppercase.

SELECT UPPER(first_name) AS uppercase_first_name
FROM employees;

✅ Output

uppercase_first_name
AMIT
NEHA
RAVI

✔ Converts text to uppercase

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5️⃣ LOWER()

Question: Convert employee last names to lowercase.

SELECT LOWER(last_name) AS lowercase_last_name
FROM employees;

✅ Output

lowercase_last_name
kumar
singh
verma

✔ Converts text to lowercase

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6️⃣ TRIM()

Question: Remove trailing spaces from customer names.

SELECT TRIM(TRAILING ' ' FROM full_name) AS trimmed_full_name
FROM customers;

✅ Output

trimmed_full_name
Amit Kumar
Neha Singh

✔ Removes unwanted spaces

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7️⃣ LEFT()

Question: Get first 5 characters of product name.

SELECT LEFT(product_name, 5) AS left_product_name
FROM products;

✅ Output

left_product_name
Lapto
Mobil
Headp

✔ Extracts characters from left

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8️⃣ RIGHT()

Question: Get last 4 characters of order number.

SELECT RIGHT(order_number, 4) AS right_order_number
FROM orders;

✅ Output

right_order_number
0001
4123

✔ Extracts characters from right

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9️⃣ REPLACE()

Question: Replace old_string with new_string.

SELECT REPLACE(description, 'old_string', 'new_string')
AS replaced_description
FROM product_descriptions;

✅ Output

replaced_description
new_string model
new new_string version

✔ Replaces text inside a string

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🧠 One-Line Memory Table (String Functions)

Function	Purpose
CONCAT	Join strings
SUBSTRING	Extract part
LENGTH	Count characters
UPPER	Uppercase
LOWER	Lowercase
TRIM	Remove spaces
LEFT	Left characters
RIGHT	Right characters
REPLACE	Replace text

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If you want next:

• Numeric functions

• Date & Time functions

• MCQs (output-based)

• All SQL functions cheat-sheet

• Hindi explanation for exams

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