Nineleaps Technology Solutions Data Analyst Interview Questions and Answers for Experienced

Q1. Difference Between Union and Union All
Ans. 
Union combines and removes duplicates, Union All combines without removing duplicates
• Union combines result sets and removes duplicates

• Union All combines result sets without removing duplicates

• Union is slower than Union All as it involves removing duplicates

• Example: SELECT column1 FROM table1 UNION SELECT column1 FROM table2;

• Example: SELECT column1 FROM table1 UNION ALL SELECT column1 FROM table2;
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Q2. SQL Execution order
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Q3. Coalesce function in SQL
Ans. 
Coalesce function in SQL is used to return the first non-null value in a list of expressions.
• Coalesce function takes multiple parameters and returns the first non-null value.

• It is commonly used to handle null values in SQL queries.

• Example: SELECT COALESCE(column_name, 'N/A') FROM table_name;
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Basics of SQL was asked, having good foundation will really help in clearing this round

Q1. Sql concepts and scenarios
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Q1. Advance level sql questions
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