🖇 Link to the recording
| Skill | Grade (out of 10) |
|---|---|
Evaluation of the candidate's appearance, including background, attire, lighting, and sound appropriateness, and assessment of their communication with the interviewer in terms of friendliness, body language, and reaction to complicated questions.
🏋️ To Work On
| SQL | ||
|---|---|---|
| Question | Exemplary Answer | Student Answer |
| What is the difference between a primary key and a foreign key? | - A primary key is used to uniquely identify each row in a table.- A foreign key is used to link tables together, establishing a relationship between them. The data referenced by the foreign key exists as a primary key in another table. | A primary key is a unique, non-nullable identifier for each record in a table. And it can be either one column or multiple. However, each table can only have one primary key. |
| What is the difference between inner join and left join? | INNER JOIN returns rows where there is a match on a certain field from both tables, LEFT JOIN returns all rows from the left table and the matched rows from the right table. | INNER: retrieves records that have matching values in both tables involved in the join. Rows must match. LEFT: retrieves all the records from the LEFT table and the MATCHED records from the right table |
| What is the purpose of GROUP BY in a SQL statement? | GROUP BY is used to aggregate rows based on certain parameters, often used with aggregate functions like COUNT, MIN, MAX, SUM, AVG | A clause in SQL that helps summarize data by categories. It’s used to group rows that have the same values in specified columns and perform aggregate functions. (COUNT, SUM, AVG, MAX, MIN). |
| Explain what a subquery is and give an example of one. | A subquery is a query nested inside another query. It's used for complex queries where the result of one query depends on another. | “Find all customers who placed an order worth more than $500.” Subqueries can appear in SELECT, FROM, or WHERE. |
| How do you use CASE statements? | A CASE statement in SQL is a fundamental decision structure leveraged in the SELECT clause. | The CASE statement in SQL allows you to perform conditional logic within a query. It works like an IF-ELSE statement in programming and is commonly used in SELECT, WHERE, ORDER BY, and GROUP BY clauses. |
| How would you explain the difference between HAVING and WHERE in SQL? | The WHERE clause is used to filter rows before any groupings are made, while the HAVING clause is used to filter data after it has been grouped (but before it is returned). | WHERE - filters rows before any grouping or aggregation happens. HAVING - filters groups after the data has been grouped (usually with GROUP BY). |
| Write me a query that returns the SUM of Salary by Department. | SELECT SUM(Salary)FROM employees GROUP BY Department | SELECT SUM(Salary) AS total_salary FROM employees GROUP BY department; |
| Write me a query that gives us all of the names of the people who work in the Sales Department that make more than $20,000. | SELECT Name FROM employees WHERE Department = ‘Sales’ AND Salary > 20000 | SELECT Name FROM employees WHERE Department = ‘Sales’ AND Salary > 20000; |
| Power BI | ||
| What is DAX and why is it important? | DAX stands for Data Analysis Expressions. It is a collection of functions, operators, and constants that can be used in a formula or expression to calculate and return values. DAX is important in Power BI for creating custom calculations and enhancing data models for more detailed and complex data analysis. | DAX stands for Data Analysis Expressions. It is a collection of functions, operators, and constants that can be used in a formula or expression to calculate and return values. DAX is important in Power BI for creating custom calculations and enhancing data models for more detailed and complex data analysis. |
| What is a model in PowerBI? | A model in Power BI is a logical representation of how data is structured and related within the tool. It is a collection of tables and relationships between them that are used to create reports and visualizations. | A model in Power BI is the structure that defines how your data tables relate to each other. It’s a collection of tables and relationships between them using DAX and/or other Metadata. |
| What are some best practices for creating effective and user-friendly dashboards in Power BI? | Effective Power BI dashboards should be clear, intuitive, and provide valuable insights at a glance. Best practices include:- Using consistent and meaningful color schemes.- Choosing the right type of chart for the data.- Avoiding clutter by not overcrowding the dashboard with too many visuals.- Ensuring that the most important information is the most prominent.- Using slicers or filters for interactive exploration.- Keeping the audience in mind and tailoring the dashboard to their needs and level of expertise. | Some best practices in designing a dashboard is that it is both insightful and easy to use are; Knowing Your Audience, Keeping it Clean & Simple, Use the Right Visual for the job, Being Intentional with Color, Make Navigation Easy, Using Tooltips and Titles Wisely, Add Smart Measures, Test with Real Users, Optimize Performance, and Telling a Story. |
| Spreadsheets | ||
| Question | Exemplary Answer | Student Answer |
| What is a VLOOKUP? | VLOOKUP is a function in Excel that allows the user to find data within another table corresponding to a particular row. | Stands for “Vertical Lookup”, and is a function used to search for a value in the first column of a table or range, and then return a value in the same row from another column. |
| Why would you create a PivotTable? | We can use PivotTables to summarize data very quickly for analysis. | PivotTables allows you to summarize, explore, and present large datasets for analysis quickly and flexibly. |
| Difference between absolute and relative reference? | An absolute reference in a spreadsheet is a fixed point that does not change when the formula is copied to another cell. Absolute references are denoted by the use of dollar signs in the cell address. A relative reference, on the other hand, changes when the formula is copied to another cell. It is relative to the position of the cell that contains the formula. | An absolute reference does not change when you copy the formula to another cell. Dollar signs ($) are used to lock both the column and the row. A relative reference in a formula changes when you copy it to another cell. No dollar signs ($) in the reference |
| What is conditional formatting and why would you use it? | Conditional formatting in Excel or other spreadsheets allows you to apply formatting (such as color, font changes, or borders) to cells based on certain conditions or criteria. Rather than manually formatting each cell, conditional formatting helps highlight key data points or trends automatically. | Conditional formatting in Excel or other spreadsheets allows you to apply formatting (such as color, font changes, or borders) to cells based on certain conditions or criteria. Rather than manually formatting each cell, conditional formatting helps highlight key data points or trends automatically. |
| How do you filter data? What are some use cases? | Filtering data in Excel allows you to display only the rows that meet certain criteria. To apply a filter, click on the Data tab, then select Filter – dropdown arrows will be added to each column header. Use these dropdown menus to filter the data. | To apply a filter, click on the Data tab, then select Filter – dropdown arrows will be added to each column header. Use these dropdown menus to filter the data. Filtering data in Excel allows you to view specific subsets of your data based on certain criteria. |
| Tableau | ||
| How can you create a calculated field in Tableau? | To create a calculated field in Tableau, you can right-click in the data pane, select "Create Calculated Field," and then enter the desired formula or expression using Tableau's calculation syntax. | To create a calculated field in Tableau, you can right-click in the data pane, select "Create Calculated Field," and then enter the desired formula or expression using Tableau's calculation syntax. It allows you to create new data based on existing data in the data sheet. |
| Explain the Difference Between Tableau Worksheet, Dashboard, Story, and a Workbook. | - A worksheet is the space where you create individual visualizations. - A dashboard is a collection of several worksheets. - A story is a sequence of worksheets or dashboards that are presented together. - A workbook is the actual Tableau file that encompasses all 3 above. | - A worksheet is the space where you create individual visualizations. - A dashboard is a collection of several worksheets. - A story is a sequence of worksheets or dashboards that are presented together. - A workbook is the actual Tableau file that encompasses all 3 above. |
| What is the difference between a Live Data Connection and Data Extract in Tableau? | A live connection in Tableau connects directly to the data source and always reflects current data, which is beneficial for real time analysis but can be slower for large datasets. An extract is a snapshot of the data taken at a specific point in time, stored in Tableau’s fast data engine, which can speed up analysis but won't reflect real-time changes. | A live connection in Tableau connects directly to the data source and always reflects current data, which is beneficial for real time analysis but can be slower for large datasets. An extract is a snapshot of the data taken at a specific point in time, stored in Tableau’s fast data engine, which can speed up analysis but won't reflect real-time changes. |
| What Parameters are utilized in a dashboard? | Parameters in Tableau are dynamic values that replace constants in calculations, filters, and reference lines. They are user inputs that control some aspect of the dashboard, such as a variable threshold or a switch between different measures. For example, a parameter could allow users to switch between viewing sales data by month, quarter, or year. | Parameters in Tableau are dynamic values that replace constants in calculations, filters, and reference lines. They are user inputs that control some aspect of the dashboard, such as a variable threshold or a switch between different measures. For example, a parameter could allow users to switch between viewing sales data by month, quarter, or year. |