ZeMoSo Technologies Senior Software Engineer Interview Questions and Answers for Freshers

Q1. What are types of joins?
Ans. 
Types of joins include inner join, outer join, left join, right join, and full join.
• Inner join: Returns rows when there is a match in both tables

• Outer join: Returns all rows when there is a match in one of the tables

• Left join: Returns all rows from the left table and the matched rows from the right table

• Right join: Returns all rows from the right table and the matched rows from the left table

• Full join: Returns rows whe
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Q2. Delete duplicates from a table?
Ans. 
Use a DELETE statement with a self-join on the table to remove duplicates.
• Use a DELETE statement with a self-join on the table to identify and remove duplicates.

• Example: DELETE t1 FROM table_name t1 INNER JOIN table_name t2 WHERE t1.id < t2.id AND t1.column_name = t2.column_name;
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Q3. What are ETL and ELT tools and what are their differences?
Ans. 
ETL and ELT tools are used for extracting, transforming, and loading data in data warehousing and analytics processes.
• ETL stands for Extract, Transform, Load and involves extracting data from various sources, transforming it into a usable format, and loading it into a data warehouse or database.

• ELT stands for Extract, Load, Transform and involves extracting data, loading it into a target system, and then transforming i...read more
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Q4. Can we add a new column in between 2 existing columns in a table? yes or no? Justify the answer
Ans. 
Yes, a new column can be added in between 2 existing columns in a table by altering the table structure.
• Yes, a new column can be added in between 2 existing columns by using the ALTER TABLE statement in SQL.

• The new column can be specified to be added after a specific existing column.

• For example, ALTER TABLE table_name ADD new_column_name datatype AFTER existing_column_name;
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Q5. Types of normalizations with brief explanation.
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Types of normalizations in databases help reduce redundancy and improve data integrity.
• First Normal Form (1NF) - Eliminates repeating groups and ensures each column contains atomic values.

• Second Normal Form (2NF) - Ensures all non-key attributes are fully functional dependent on the primary key.

• Third Normal Form (3NF) - Removes transitive dependencies by moving non-key attributes to separate tables.

• Boyce-Codd Normal Fo...read more
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Q1. Basics of oops concepts
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Q2. SQL queries based on joins, views and stored procedures
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Q3. Difference between SP and A function
Ans. 
SP is a stored procedure in a database, while a function is a piece of code that performs a specific task.
• SP is precompiled and stored in the database, while a function is compiled and executed at runtime.

• Functions can return a value, while SPs can return multiple result sets.

• Functions can be used in SQL queries, while SPs are called using EXECUTE statement.
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Q4. What are views, why use them and what are the types.
Ans. 
Views in databases are virtual tables that display data from one or more tables based on a query.
• Views are used to simplify complex queries by storing them as a virtual table.

• They can hide the complexity of underlying tables and provide a layer of security by restricting access to certain columns.

• Types of views include simple views, complex views, materialized views, and indexed views.
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Q5. Top-down vs bottom-up programming approach.
Ans. 
Top-down focuses on breaking down the problem into smaller parts, while bottom-up starts with small components and builds up.
• Top-down starts with a high-level overview and breaks it down into smaller components.

• Bottom-up starts with small components and gradually builds up to create a complete system.

• Top-down is more structured and easier to plan, while bottom-up is more flexible and iterative.

• Examples: Top-down - wate
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Q1. About the project. and asked what i did in project. how to create schema in pyspark. what is ADE. what are the difficulties i faced in project. what is spark submit command how we write sparksubmit command...read more
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Q2. No of occurrences of letter in a string.
Ans. 
Count occurrences of a letter in a string.
• Iterate through each character in the string and count occurrences of the specified letter.

• Use a hashmap to store the count of each letter.

• Handle both uppercase and lowercase letters to ensure accurate counting.
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Q1. Form based JS questions. String questions in javascript
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Q2. React interview questions with some state management follow up questions.
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Duration was 1 hour, Topics covered were DSA, Concurrency in golang, Databse questions