PostgreSQL Insert Data

PostgreSQL Tutorial

🐘 PostgreSQL INSERT Data

In PostgreSQL, the INSERT statement is used to add new records (rows) into a table.
This is one of the most important SQL operations and is frequently asked in interviews.

1️⃣ What is INSERT in PostgreSQL?

The INSERT INTO statement:

  • Adds new rows to a table

  • Can insert single or multiple records

  • Can insert data from another table (INSERT SELECT)

2️⃣ Basic INSERT Syntax ⭐



 

3️⃣ Example Table



 

4️⃣ Insert Single Row ⭐



 

✔ Inserts one record
✔ id is auto-generated because of SERIAL

5️⃣ Insert Multiple Rows ⭐⭐



 

✔ Faster than multiple single inserts
✔ Interview favorite

6️⃣ Insert Without Column Names ❌ (Not Recommended)



 

⚠️ Column order must match table structure
📌 Avoid this in real projects

7️⃣ Insert Partial Data (NULL Values) ⭐



 

✔ Missing columns become NULL
✔ Works only if column allows NULL

8️⃣ INSERT with DEFAULT Value ⭐



 

✔ Uses column default value

9️⃣ INSERT Using SELECT (Advanced) ⭐⭐



 

✔ Copies data from another table
✔ Very common in data migration

🔟 RETURNING Clause (PostgreSQL Special ⭐)



 

✔ Returns generated ID
✔ PostgreSQL-specific feature
✔ Interview bonus point

1️⃣1️⃣ Check Inserted Data

SELECT * FROM users;

1️⃣2️⃣ Common INSERT Errors ❌

❌ Column/value count mismatch
❌ Data type mismatch
❌ Violating NOT NULL / UNIQUE constraint
❌ Forgetting quotes for strings

📌 Interview Questions & MCQs

Q1. Which command is used to insert data?

A) ADD
B) INSERT
C) PUT
D) UPDATE

✅ Answer: B

Q2. How to insert multiple rows?

A) Multiple INSERT statements
B) VALUES with commas
C) UPDATE
D) JOIN

✅ Answer: B

Q3. Which PostgreSQL feature returns inserted ID?

A) LAST_ID
B) AUTO_ID
C) RETURNING
D) SERIAL

✅ Answer: C

Q4. If column is missing in INSERT?

A) Error always
B) Gets NULL
C) Gets 0
D) Gets ignored

✅ Answer: B (if NULL allowed)

Q5. Is INSERT SELECT allowed in PostgreSQL?

A) Yes
B) No

✅ Answer: A

🔥 Real-Life Use Cases

✔ User registration
✔ Order creation
✔ Log storage
✔ Data migration
✔ API backends

✅ Summary

  • Use INSERT INTO to add data

  • Supports single & multiple inserts

  • SERIAL auto-generates IDs

  • RETURNING is PostgreSQL-specific

  • INSERT SELECT useful for migrations

  • Core topic for PostgreSQL exams & interviews

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