SQL CONCAT() — সম্পূর্ণ ২ ঘন্টার লাইভ ক্লাস নোট

01

কেন CONCAT()?

১৫ মিনিট

employee_id	first_name	last_name
101	Rahim	Khan
102	Karim	Hossain
103	Jannat	Ahmed

জিজ্ঞেস

দুই column আলাদা — HR চায় Rahim Khan। কীভাবে একসাথে দেখাব?

first_name + last_name → Full Name

CONCAT() = একাধিক value জুড়ে একটি combined text/value তৈরি করে।

02

Real-life Examples

১০ মিনিট

Rahim + Khan → Rahim Khan 12 + Dhanmondi + Dhaka → 12 Dhanmondi Dhaka Apple + iPhone + 15 → Apple iPhone 15 101 + Rahim Khan → 101 - Rahim Khan C001 + Rahim → C001 - Rahim Multiple Values → CONCAT() → One Combined Result

03

CONCAT() কী?

১০ মিনিট

CONCAT(value1, value2, value3, ...)

CONCAT() │ Value 1 · Value 2 · Value 3 ↓ Combined Result

Function name · parentheses · values · comma · অনেক argument।

04

প্রথম উদাহরণ

১০ মিনিট

SELECT CONCAT('Hello', 'World');

HelloWorld

SELECT CONCAT('Hello', ' ', 'World');

Hello World

Space নিজেও একটা value — CONCAT()-এ আলাদা দিয়ে দিতে হয়।

05

Table Columns

১৫ মিনিট

CREATE TABLE employees ( employee_id INT, first_name VARCHAR(50), last_name VARCHAR(50) ); INSERT INTO employees VALUES (101,'Rahim','Khan'), (102,'Karim','Hossain'), (103,'Jannat','Ahmed'), (104,'Sakib','Hasan'), (105,'Nadia','Rahman');

SELECT CONCAT(first_name, last_name) FROM employees;

RahimKhan · KarimHossain · …

সমস্যা?

মাঝে space নেই।

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

Rahim Khan · Karim Hossain · …

06

অনেক Argument

১০ মিনিট

SELECT CONCAT( 'Employee: ', employee_id, ' - ', first_name, ' ', last_name ) AS employee_info FROM employees;

Employee: 101 - Rahim Khan Employee: 102 - Karim Hossain

'Employee: ' + id + ' - ' + first + ' ' + last → Final

07

Text + Column + Number

১০ মিনিট

SELECT CONCAT('Employee ID: ', employee_id) AS employee_id_label FROM employees; SELECT CONCAT( 'Employee ', employee_id, ': ', first_name ) AS employee_label FROM employees;

Employee ID: 101 Employee 101: Rahim

08

Custom Separators

১০ মিনিট

Useful separators: ' ' ', ' ' - ' ' | ' ': ' '/'

SELECT CONCAT(first_name, ' ', last_name) FROM employees; SELECT CONCAT(first_name, ' - ', last_name) FROM employees; SELECT CONCAT(first_name, ' | ', last_name) FROM employees; SELECT CONCAT(first_name, ': ', last_name) FROM employees;

CONCAT() নিজে separator বানায় না — আমাদের দিতে হয়।

09

৩, ৪, ৫+ Values

১০ মিনিট

SELECT CONCAT(first_name, ' ', last_name, ' - Employee') FROM employees; SELECT CONCAT(first_name, ' ', last_name, ' - ', employee_id) FROM employees; SELECT CONCAT( house_no, ', ', road, ', ', area, ', ', city, ', ', country ) AS full_address FROM customers;

বাম থেকে ডানে argument ধরে জোড়ে।

10

Alias (সংক্ষেপ)

৫ মিনিট

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

Without alias → ugly column name With alias → full_name (report-friendly)

11

Business Reports

১০ মিনিট

Domain	CONCAT idea	Purpose
HR	first + ' ' + last	Full name
E-com	brand + ' ' + product + ' ' + model	Display name
Support	id + ' - ' + name	Customer label
Bank	code + ' - ' + branch	Branch label
Hospital	id + ' - ' + patient	Patient label
Logistics	order + ' - ' + tracking	Tracking label

12

Full Address Lab

১০ মিনিট

customer_id	house	road	area	city
1	12	Road 5	Dhanmondi	Dhaka
2	25	Road 2	Banani	Dhaka

SELECT CONCAT( house, ', ', road, ', ', area, ', ', city ) AS full_address FROM customers;

12, Road 5, Dhanmondi, Dhaka 25, Road 2, Banani, Dhaka

13

Product Label

১০ মিনিট

brand	product	model
Apple	iPhone	15
Samsung	Galaxy	S24
Dell	Inspiron	15

SELECT CONCAT(brand, ' ', product, ' ', model) AS product_label FROM products;

Apple iPhone 15 Samsung Galaxy S24 Dell Inspiron 15

14

Generated Messages

১০ মিনিট

SELECT CONCAT( 'Hello ', first_name, ', welcome to our company!' ) AS message FROM employees; SELECT CONCAT( 'Employee ', employee_id, ' is ', first_name, ' ', last_name ) AS message FROM employees;

Hello Rahim, welcome to our company! Employee 101 is Rahim Khan

15

CONCAT + Expression

১০ মিনিট

SELECT CONCAT( 'Employee ID: ', employee_id + 1000 ) AS new_label FROM employees;

এখানে ফোকাস CONCAT — arithmetic আলাদা পাঠ নয়।

16

Predict the Output (১৫)

১০ মিনিট

Predict: CONCAT('Data','Science')

DataScience

Predict: CONCAT('Data',' ','Science')

Data Science

Predict: CONCAT('SQL',' ','Class',' ','2026')

SQL Class 2026

Predict: CONCAT('A','-','B')

A-B

Predict: CONCAT('A',' | ','B')

A | B

Predict: CONCAT('Hi ',first) if first=Rahim

Hi Rahim

Predict: CONCAT(101,' - ',name) name=Rahim

101 - Rahim

Predict: CONCAT(first,last) Rahim+Khan

RahimKhan

Predict: CONCAT(first,' ',last)

Rahim Khan

Predict: CONCAT('ID:',employee_id) id=101

ID:101

Predict: CONCAT('ID: ',employee_id)

ID: 101

Predict: CONCAT('X',', ','Y')

X, Y

Predict: CONCAT('Hello','','World')

HelloWorld (empty string)

Predict: 4 values 'A',' ','B','!'

A B!

Predict: CONCAT('Emp ',id,': ',first) 101 Rahim

Emp 101: Rahim

17

Find the Mistake (১০)

১০ মিনিট

Bug: CONCAT(first_name last_name)

Comma missing between args

Bug: CONCAT('first_name','last_name')

Quotes → literal text, not columns

Bug: CONCAT(first_name ' ' last_name)

Missing commas around space

Bug: CONCAT(first_name, last_name) no space

Forgot ' ' separator

Bug: CONCAT(first_name,,last_name)

Empty/extra comma confuse

Bug: CONCAT first_name, last_name)

Missing opening (

Bug: CONCAT(first_name, ' -' last_name)

Missing comma after separator

Bug: CONCAT(first_name, '-', -, last_name)

Invalid bare hyphen

Bug: alias missing for report

Add AS full_name

Bug: CONCAT(first_name, ' ', last_name) too many spaces?

Check separator — maybe want single space

18

CONCAT Mistakes

৮ মিনিট

Comma ভুলে
Fixed text-এ quotes ভুলে
Space value ভুলে
Column নাম quotes-এ
Parentheses ভুল
Separator ভুল জায়গায়
অপ্রয়োজনীয় separator
অনেক confusing argument
খারাপ alias
Output না চেক করা

Pattern

Wrong → Why? → Correct → Expected

19

Pattern Library

৮ মিনিট

Full Name:     CONCAT(first_name, ' ', last_name)
ID + Name:      CONCAT(employee_id, ' - ', first_name)
ID + Full:      CONCAT(employee_id, ' - ', first_name, ' ', last_name)
Product:        CONCAT(brand, ' ', product, ' ', model)
Address:        CONCAT(house, ', ', road, ', ', city)
Status:         CONCAT('Status: ', status)
Greeting:       CONCAT('Hello ', first_name)
Report:         CONCAT('Total Sales: ', total_sales)

20

Mini Project — Label Generator

১৫ মিনিট

২০+ employees: employee_id, first_name, last_name, department, designation, city।

Full name
101 - Rahim Khan
Rahim Khan | Software Engineer | IT
Rahim Khan | Dhaka
EMP-101 | Rahim Khan | Software Engineer | Dhaka
Hello Rahim Khan!
Department: IT

SELECT CONCAT(first_name, ' ', last_name) AS full_name, CONCAT(employee_id, ' - ', first_name, ' ', last_name) AS id_name, CONCAT(first_name, ' ', last_name, ' | ', designation, ' | ', department) AS profile_label, CONCAT('EMP-', employee_id, ' | ', first_name, ' ', last_name, ' | ', designation, ' | ', city) AS complete_label, CONCAT('Hello ', first_name, ' ', last_name, '!') AS greeting, CONCAT('Department: ', department) AS dept_label FROM employees;

21

Professional Thinking

৮ মিনিট

What info do I have? → Which values together? → What separator? → Write CONCAT() → Correct order → Readable alias → Check output

22

Interview (২০)

১২ মিনিট

IV 1. CONCAT কী?

একাধিক value জোড়া · উদা: full name · ইউজ: labels

IV 2. কেন ব্যবহার?

আলাদা column একসাথে দেখাতে · ফলো: separator · ইউজ: reports

IV 3. First+last?

CONCAT(first,' ',last)

IV 4. Space কীভাবে?

' ' হিসেবে আলাদা argument

IV 5. Number + string?

হ্যাঁ — CONCAT মিলিয়ে দেয়

IV 6. কত value?

একাধিক (MySQL অনেক argument নেয়)

IV 7. Column quotes-এ?

Literal text হয় — column নয়

IV 8. Full address?

CONCAT(house,', ',road,', ',city)

IV 9. Product label?

CONCAT(brand,' ',product,' ',model)

IV 10. Employee label?

CONCAT(id,' - ',first,' ',last)

IV 11. Comma কেন?

Arguments আলাদা করতে

IV 12. Quotes কেন?

Fixed text চিহ্নিত করতে

IV 13. Hyphen?

CONCAT(a,' - ',b)

IV 14. Comma separator?

CONCAT(a,', ',b)

IV 15. Greeting?

CONCAT('Hello ',first_name)

IV 16. ৫ column?

প্রতিটি + separator বাম→ডান

IV 17. Report-এ?

readable label columns

IV 18. Value vs column?

quotes=literal · no quotes=column

IV 19. Readable output?

separator + AS alias

IV 20. Real use?

HR name, e-com title, ticket labels

23

MCQ (২০)

১০ মিনিট

MCQ 1. CONCAT does? A) sort B) join values C) delete D) count

B

MCQ 2. CONCAT('A','B')? A) A B B) AB C) A,B D) error

B

MCQ 3. Space how? A) automatic B) pass ' ' C) TRIM D) JOIN

B

MCQ 4. Missing comma? A) OK B) syntax error/wrong C) auto-fix D) NULL

B

MCQ 5. 'first_name' in quotes? A) column B) literal text C) number D) table

B

MCQ 6. CONCAT(first,last) Rahim Khan →? A) Rahim Khan B) RahimKhan C) error D) NULL

B

MCQ 7. Separator built-in? A) yes always B) no — you pass it C) only comma D) only space

B

MCQ 8. Can mix number? A) no B) yes C) only INT D) only FLOAT

B

MCQ 9. Alias role? A) rename result col B) join tables C) delete D) sort

A

MCQ 10. CONCAT(a,' - ',b)? A) a-b B) a - b C) a,b D) ab

B

MCQ 11. CONCAT(a,' | ',b)? A) a|b B) a | b C) a,b D) ab

B

MCQ 12. Order of args? A) right→left B) left→right C) random D) alpha

B

MCQ 13. Full name pattern?

CONCAT(first,' ',last)

MCQ 14. ID label pattern?

CONCAT(id,' - ',name)

MCQ 15. Address commas?

CONCAT(h,', ',r,', ',c)

MCQ 16. Greeting?

CONCAT('Hello ',first)

MCQ 17. Product 3 parts?

CONCAT(brand,' ',product,' ',model)

MCQ 18. Expression inside? A) never B) allowed e.g. id+1000 C) only SUM D) only JOIN

B

MCQ 19. Focus of this class? A) TRIM B) CONCAT only C) LIKE D) JOIN

B

MCQ 20. Check output why?

Verify separators/order before using in reports

24

Classroom Practice (১৫)

১২ মিনিট

Ex 1 — Join two fixed texts

SELECT CONCAT('Hello','World')

Ex 2 — First + last

CONCAT(first_name,last_name)

Ex 3 — Add space

CONCAT(first_name,' ',last_name)

Ex 4 — Add hyphen

CONCAT(first_name,' - ',last_name)

Ex 5 — Add comma

CONCAT(city,', ',country)

Ex 6 — Three columns

CONCAT(a,' ',b,' ',c)

Ex 7 — Four columns

CONCAT(a,' ',b,' - ',c,' ',d)

Ex 8 — Text + number

CONCAT('ID: ',employee_id)

Ex 9 — Employee label

CONCAT(employee_id,' - ',first_name,' ',last_name)

Ex 10 — Product label

CONCAT(brand,' ',product,' ',model)

Ex 11 — Full address

CONCAT(house,', ',road,', ',area,', ',city)

Ex 12 — Customer label

CONCAT(customer_id,' - ',customer_name)

Ex 13 — Profile label

CONCAT(first,' ',last,' | ',designation,' | ',department)

Ex 14 — Greeting

CONCAT('Hello ',first_name,' ',last_name,'!')

Ex 15 — Business report label

CONCAT('EMP-',id,' | ',first,' ',last,' | ',city)

25

Cheat Sheet + Memory Map

৫ মিনিট

CONCAT() → একাধিক value একসাথে
CONCAT(a, b) → a + b
CONCAT(a, ' ', b) → a + space + b
CONCAT(a, ' - ', b) → a + hyphen + b
CONCAT(a, ', ', b) → a + comma + b

CONCAT()
  TEXT · COLUMN · NUMBER
       ↓
 Optional Separator (you provide)
       ↓
 Combined Result → NAME / ADDRESS / LABEL

CONCAT() = একাধিক value-কে একসাথে জোড়া লাগানো।

TRIM / LOWER / CONCAT_WS / LIKE ইত্যাদি — অন্য module-এর বিষয়।

একাধিক value একসাথে — SQL CONCAT()

বিষয়সূচী

কেন CONCAT()?

Real-life Examples

CONCAT() কী?

প্রথম উদাহরণ

Table Columns

অনেক Argument

Text + Column + Number

Custom Separators

৩, ৪, ৫+ Values

Alias (সংক্ষেপ)

Business Reports

Full Address Lab

Product Label

Generated Messages

CONCAT + Expression

Predict the Output (১৫)

Find the Mistake (১০)

CONCAT Mistakes

Pattern Library

Mini Project — Label Generator

Professional Thinking

Interview (২০)

MCQ (২০)

Classroom Practice (১৫)

Cheat Sheet + Memory Map