Lesson 05 � Data Manipulation

TABLE MEIN DATA
DAALNA SEEKHO.

Database banana baad mein aata hai�pehle data daalna padta hai. Naye students, naye orders, naye records�sab INSERT INTO se add hote hain. Bina data ke table khaali hai, aur query bhi kuch nahi degi.

WHY: INSERT kyun zaruri hai?

Socho aapne ek school database banaya�students table tayyar hai columns ke saath. Lekin table khaali hai. Ab kya✓ INSERT INTO se aap naye rows add karoge. Ye sabse pehla kaam hai database mein�data daalna. Bina INSERT ke aap SELECT, WHERE, ORDER BY�kuch bhi nahi kar paoge kyunki kuch hoga hi nahi table mein.

HOW: INSERT ka syntax

INSERT INTO do tarikon se use hota hai�columns specify karke ya bina specify kiye. Dono tarike dekhte hain.

1. Single row insert

Ek naya student add karo�columns aur values dono likho:

INSERT INTO students (id, name, age, course, marks)
VALUES (4, 'Neha', 20, 'AI', 88.0);

2. Multiple rows insert

Tinn naye students ek saath add karo�comma se separate karo:

INSERT INTO students (id, name, age, course, marks) VALUES
(5, 'Vikram', 24, 'ML', 91.5),
(6, 'Sneha', 22, 'Python', 84.0),
(7, 'Amit', 23, 'Data Science', 79.5);

3. Bina columns ke insert

Agar saare columns ki value de rahe ho (table ki column order mein), toh columns likhne ki zaroorat nahi:

INSERT INTO students VALUES (8, 'Riya', 21, 'SQL', 95.0);

4. Default values

Agar column ka default value hai (jaise created_at ka CURRENT_TIMESTAMP), toh uss column ko skip karo:

INSERT INTO students (id, name, age, course, marks)
VALUES (9, 'Karan', 19, 'DS', 82.0);

5. Another table se insert

Ek table se data utha ke doosre mein daalo�backup banana ho ya filtered data chahiye ho:

INSERT INTO backup_students
SELECT * FROM students WHERE marks > 90;

6. INSERT with SELECT

Doosre table se specific columns utha ke insert karo:

INSERT INTO top_students (id, name, marks)
SELECT id, name, marks FROM students WHERE marks > 85;

Syntax quick reference

-- Single row
INSERT INTO table_name (col1, col2, col3)
VALUES (val1, val2, val3);

-- Multiple rows
INSERT INTO table_name (col1, col2, col3) VALUES
(val1a, val2a, val3a),
(val1b, val2b, val3b),
(val1c, val2c, val3c);

-- All columns (risky)
INSERT INTO table_name
VALUES (val1, val2, val3);

-- From another table
INSERT INTO target_table (col1, col2)
SELECT col1, col2 FROM source_table WHERE condition;

Try it: naye students add karo

Neeche diye gaye SQL queries ko editor mein modify karo aur dekho output kaise badalta hai. Pehle single row insert try karo, phir multiple rows.

Common beginner mistakes

• Column-value mismatch: Agar 5 columns likhe ho aur 4 values diye ho�error aayega. Hamesha count match karo.
• String mein double quotes: VALUES (1, "Neha") galat hai. Strings hamesha single quotes mein: 'Neha'.
• Duplicate primary key: Agar id=4 pehle se hai aur phir se daalte ho�error aayega. UNIQUE constraint violation hota hai.
• Column order bhoolna: Bina columns ke INSERT karna risky hai. Agar table mein column add ho gaya toh values galat jagah chali jayengi.
• Semicolon bhoolna: Har statement ke baad ; lagana zaroori hai�warna query complete nahi manegi.