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75+ SQL Interview Questions

⇩

 Level: Beginner to Medium
Topics:

➊ Introduction to RDBMS
➋ Normalisation
➌ Introduction to SQL
➍ Tables and Fields
➎ Constraints
➏ DDL
➐ DML & DQL
➑ Joins
➊ Introduction to RDBMS

➀ What is a Database?
➁ What are different types of Databases?
➂ What is DBMS?
➃ What is difference between Database and DBMS?
➄ What is RDBMS?
➅ Which are popular RDBMS vendors?
➆ What is ACID property in Database?
➋ Normalisation

➀ What is Normalisation?
➁ Why is Normalisation necessary?
➂ What are the disadvantages of not performing Normalisation?
➃ What are different Normal Forms (NF)?
➄ What is Denormalisation?
➌ Introduction to SQL

➀ What is SQL?
➁ What is the use of SQL?
➂ Is SQL a programming language?
➃ What are the different parts of SQL?
Or,
➄ Group SQL commands in different parts.
➅ What is DDL?
➆ What is DML?
➇ What is DQL?
➈ What is DCL?
➉ What is TCL?
➍ Tables and Fields

➀ What is a Table?
➁ What is a field in a Table?
➂ Write a SQL command to create a Table.
➃ How to change the name of a Table?
➄ How to truncate a table?
➅ How to drop a table?
➎ Constraints

➀ What is a constraint?
➁ What are different levels of constraints?
➂ Give examples of various constraints?
➃ What is a primary key?
➄ What is a unique key?
➅ Difference between a primary key and a unique key.
➆ What is a foreign key?
➇ What is NULL value?
➈ What is NOT NULL constraint?
➉ Is blank space or Zero (0) same as NULL?
➏ DDL

➀ Give some examples of DDL commands
➁ Write the syntax of creating a table
➂ How to specify the default value for a column?
➃ How to specify a foreign key?
➄ How to specify a unique key?
➅ How to specify multiple columns as the primary key?
➆ What are different constraints you can add to a column while creating a table?
➇ How to create a copy of a table? (both structure and, data)
➈ You have 'n' tables and asked to create a separate table which will contain a few columns from these tables with data being copied.
➉ What is SELECT INTO used for? (In SQL Server)
➀➀ Difference between ALTER and RENAME
➀➁ Can a previously nullable column be altered to a NOT NULL column? If yes, explain the steps.
➐ DML & DQL

➀ How to insert rows into a table?
➁ What are different syntaxes for inserting records into a table?
➂ What is the syntax to insert multiple records at a time?
➃ How to update data in a table?
➄ How to delete a row in a table?
➅ Difference between DELETE and TRUNCATE?
➆ Explain how DML operations are performed on a View.
Or,
➇ Are Views used only for SELECT queries?
➈ How to fetch rows of a table?
➉ What is a query condition? How to write it in SQL?
➀➀ How to sort the fetched records?
➀➁ What is grouping? How to write in SQL?
➀➂ How to find how many records are being fetched?
➀➃ How to find the maximum and minimum value for a field in fetched records?
➀➄ How to sum values in a field for all records?
➑ Joins

➀ What is a join in SQL?
➁ What are the different types of joins?
➂ What is Inner Join?
➃ What is Left Outer Join?
➄ What is Right Outer Join?
➅ What is Full Outer Join?
➆ What is Cross Join?
➇ What is a Self Join?
➈ What is Equi Join?
➉ What is Natural Join?

➀➀ Given a query in Cross Join, convert it into an Inner Join.

➀➁ Given a query in Right Outer Join, convert it into a Left Outer Join.
➀➂ Convert an Inner Join into an Equi Join.
Or,
➀➃ What is required to convert an Inner Join into an Equi Join?

➀➄ What should be taken care of to improve the performance of queries containing Joins.
🚥 Disclaimer

⬘ The questions covered here are mostly conceptual

⬗ I never claim only these types of questions are/should be asked during interviews

⬙ For interviews, you should have fundamentals strong. And you should be able to provide solutions to practical problems.
Hey 👋

I am a Tech Educator and, Mentor from India 🇮🇳

I am sharing Tutorials, Tips, Techniques, Infographics, Cheat Sheets, Practice Questions, Project Ideas and Roadmaps on Web Development, DSA and, Databases.

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Swapna Kumar Panda
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👩‍💻 75+ SQL Practice Questions

❍ Oracle
❍ MySQL
❍ SQL Server
❍ PostgreSQL
❍ SQLite

⇩

Topics covered:

➊ Table
➋ Constraints
➀ Primary Key
➁ Unique
➂ Not Null
➃ Default
➄ Check
➅ Foreign Key
➌ Insert, Update, Delete
➍ Select

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➁ Add a field to an existing table.

➂ Modify a field's data type of a table.

➃ Rename a field's name.

➄ Remove a field from a table.

➅ Rename a table's name.

➆ Drop a table.

➋ Constraints

➀ Primary Key
➁ Unique
➂ Not Null
➃ Default
➄ Check
➅ Foreign Key

➋.➀ Primary Key

➤ Create a Table with
➀ a single field as the primary key
➁ 2 or, more fields as the primary key
...

➤ Add a primary key to an existing table
➂ for a single field
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JavaScript First, Then React?
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@swapnakpanda
🛣 Beginner's Roadmap for Front-End

HTML & CSS → 👩‍💻 → JavaScript → 👩‍💻
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JavaScript is essential. You should start with basics and move to complex subjects.

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