Zifo RnD Solutions Associate Data Analyst Interview Questions and Answers

Q1. Difference between Primary Key and Unique Key ?
Ans. 
Primary key uniquely identifies each record in a table, while Unique key allows only unique values but can have null values.
• Primary key enforces uniqueness and not null constraint on a column

• Primary key can consist of multiple columns

• Unique key allows only unique values but can have null values

• Unique key can be applied to multiple columns as well
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Q1. SQL Questions on Aggregations
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The sql questions were hard

Q1. SQL and excel questions intermediate
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Q1. Highlight the odd cells in excel
Ans. 
Use conditional formatting to highlight odd cells in Excel
• Select the range of cells you want to highlight

• Go to the 'Home' tab and click on 'Conditional Formatting'

• Choose 'New Rule' and select 'Use a formula to determine which cells to format'

• Enter the formula '=MOD(A1,2)=1' (assuming A1 is the top-left cell of your selected range)

• Choose the formatting style you want for the odd cells
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Q2. What are Joins in SQL, explain different joins and their outputs
Ans. 
Joins in SQL are used to combine rows from two or more tables based on a related column between them.
• Types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN

• INNER JOIN returns rows when there is at least one match in both 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

• FU...read more
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Q3. Query to give running sum of salary
Ans. 
Use window function to calculate running sum of salary in SQL
• Use window function like SUM() with OVER() clause

• Partition the data by employee ID if needed

• Order the data by date or any other relevant column
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Easy SQL questions related to sub query

SQL moderate questions related to joins and window functions

Q1. Asked about specific tools related to requirement
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The first round was a combination of MCQs and SQL Coding test. It consisted of 23 MCQs on SQL, 10 MCQs on Power BI and 5 SQL Coding questions.

Q1. Simple questions on SQL were asked.
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Q1. What is pivot table in Excel?
Ans. 
A pivot table in Excel is a data summarization tool that allows you to reorganize and summarize selected columns and rows of data.
• Pivot tables allow you to analyze and summarize large amounts of data in a spreadsheet.

• You can easily rearrange the layout of the data to view it from different perspectives.

• Pivot tables can perform functions like sum, average, count, and more on the data.

• They are useful for creating reports...read more
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Q2. What is 'Data Validation' in Excel?
Ans. 
Data Validation in Excel ensures that data entered in a cell meets certain criteria or conditions.
• Data Validation allows you to set rules for what can be entered in a cell, such as a range of values, a list of items, or a custom formula.

• Examples of Data Validation include setting a drop-down list of options for a cell, restricting input to a certain number range, or ensuring dates are entered in a specific format.

• Data ...read more
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Q3. What is the order of execution of an SQL query?
Ans. 
The order of execution of an SQL query involves multiple steps to retrieve data from a database.
• 1. Parsing: The SQL query is first parsed to check for syntax errors.

• 2. Optimization: The query optimizer creates an execution plan to determine the most efficient way to retrieve data.

• 3. Compilation: The optimized query is compiled into an executable form.

• 4. Execution: The compiled query is executed by the database engine t...read more
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Q4. What is the difference between Tree Map and Heatmap in Tableau?
Ans. 
Tree Map visualizes hierarchical data using nested rectangles, while Heatmap displays data values using color gradients.
• Tree Map displays data hierarchically with nested rectangles, where the size and color represent different measures.

• Heatmap visualizes data values using color gradients, with darker colors indicating higher values.

• Tree Map is useful for showing hierarchical data structures, while Heatmap is effective ...read more
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Q5. What is the difference between 'Extract Data' and 'Live Connection' in Tableau?
Ans. 
Extract Data saves a snapshot of data in Tableau workbook, while Live Connection directly connects to data source.
• Extract Data creates a static copy of data in Tableau workbook, while Live Connection directly queries data source in real-time.

• Extract Data is useful for working offline or with small datasets, while Live Connection is ideal for large datasets or when data is frequently updated.

• Extract Data can improve per...read more
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