Data Analyst Interview Resources
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Show more📈 Analytical overview of Telegram channel Data Analyst Interview Resources
Channel Data Analyst Interview Resources (@dataanalystinterview) in the English language segment is an active participant. Currently, the community unites 52 611 subscribers, ranking 3 250 in the Education category and 6 703 in the India region.
📊 Audience metrics and dynamics
Since its creation on невідомо, the project has demonstrated rapid growth, gathering an audience of 52 611 subscribers.
According to the latest data from 28 August, 2026, the channel demonstrates stable activity. Although there has been a change in the number of participants by 18 over the last 30 days and by -7 over the last 24 hours, overall reach remains high.
- Verification status: Not verified
- Engagement rate (ER): The average audience engagement rate is 1.94%. Within the first 24 hours after publication, content typically collects 0.83% reactions from the total number of subscribers.
- Post reach: On average, each post receives 1 019 views. Within the first day, a publication typically gains 435 views.
- Reactions and interaction: The audience actively supports content: the average number of reactions per post is 2.
- Thematic interests: Content is focused on key topics such as sql, row, |--, dataset, visualization.
📝 Description and content policy
The author describes the resource as a platform for expressing subjective opinions:
“Join our telegram channel to learn how data analysis can reveal fascinating patterns, trends, and stories hidden within the numbers! 📊
For ads & suggestions: @love_data”
Thanks to the high frequency of updates (latest data received on 29 August, 2026), the channel maintains relevance and a high level of publication reach. Analytics show that the audience actively interacts with content, making it an important point of influence in the Education category.
SELECT MAX(salary) AS second_highest
FROM employee
WHERE salary < (SELECT MAX(salary) FROM employee);
(Handles ties; alternative: use DENSE_RANK() for modern SQL.)
2️⃣ Get the top 3 products by revenue from sales table.
SELECT product_id, SUM(revenue) AS total_revenue
FROM sales
GROUP BY product_id
ORDER BY total_revenue DESC
LIMIT 3;
3️⃣ Use JOIN to combine customer and order data.
SELECT c.customer_name, o.order_date, o.amount
FROM customers c
INNER JOIN orders o ON c.customer_id = o.customer_id;
(Use INNER for matches; LEFT for all customers.)
4️⃣ Difference between WHERE and HAVING?
WHERE filters rows before grouping; HAVING filters after GROUP BY (e.g., on aggregates like SUM). WHERE is for individual rows, HAVING for grouped results.
5️⃣ Explain INDEX and how it improves performance.
An INDEX speeds up data retrieval by creating a data structure (like a B-tree) for quick lookups on columns. It reduces full table scans but adds overhead on inserts/updates.
🟦 Excel / Power BI
1️⃣ How would you clean messy data in Excel?
Use Text to Columns for splitting, Find & Replace for errors, Remove Duplicates tool, and Power Query for advanced ETL (e.g., trim spaces, handle dates).
2️⃣ What is the difference between Pivot Table and Power Pivot?
Pivot Tables summarize data visually; Power Pivot adds data modeling (relationships, DAX) for larger datasets and complex calculations beyond standard Pivots.
3️⃣ Explain DAX measures vs calculated columns.
Measures are dynamic formulas (e.g., SUM for totals) computed on-the-fly for reports; calculated columns are static, row-by-row computations stored in the model.
4️⃣ How to handle missing values in Power BI?
Use Power Query to replace nulls (e.g., with averages via "Replace Values"), or DAX like IF(ISBLANK()) in visuals. For viz, filter them out or use "Show items with no data."
5️⃣ Create a KPI visual comparing actual vs target sales.
In Power BI, drag KPI visual, add actual sales to Value, target to Target, and trend metric. Set variance to show % difference—green/red indicators highlight performance.
🟩 Python
1️⃣ Write a function to remove outliers from a list using IQR.
import numpy as np
def remove_outliers(data):
Q1 = np.percentile(data, 25)
Q3 = np.percentile(data, 75)
IQR = Q3 - Q1
lower = Q1 - 1.5 * IQR
upper = Q3 + 1.5 * IQR
return [x for x in data if lower <= x <= upper]
2️⃣ Convert a nested list to a flat list.
nested = [[1, 2], [3, 4]]
flat = [item for sublist in nested for item in sublist]
# Or: import itertools; list(itertools.chain.from_iterable(nested))
3️⃣ Read a CSV file and count rows with nulls.
import pandas as pd
df = pd.read_csv('file.csv')
null_counts = df.isnull().sum(axis=1)
print(null_counts[null_counts > 0].count()) # Rows with at least one null
4️⃣ How do you handle missing data in pandas?
Use df.fillna(value) for imputation (e.g., mean), df.dropna() to drop rows/cols, or df.interpolate() for time series. Check with df.isnull().sum() first.
5️⃣ Explain the difference between loc[] and iloc[].
loc[] uses labels (e.g., df.loc['row_label']) for selection; iloc[] uses integer positions (e.g., df.iloc[0:2])—great for slicing by index.
💡 Pro Tip: Practice with mock datasets from Kaggle + build dashboards on Power BI to showcase in interviews. These hit the core skills employers test in 2025!
💬 Tap ❤️ for detailed answers!
SQL's often the make-or-break—want code breakdowns or Python tips next? 😊.dropna(), .fillna() functions to do this easily.
4. What are list comprehensions and how are they useful?
Concise syntax to create lists from iterables using a single readable line, often replacing loops for cleaner and faster code.
Example: [x**2 for x in range(5)] → ``
5. Explain Pandas DataFrame and Series.
⦁ Series: 1D labeled array, like a column.
⦁ DataFrame: 2D labeled data structure with rows and columns, like a spreadsheet.
6. How do you read data from different file formats (CSV, Excel, JSON) in Python?
Using Pandas:
⦁ CSV: pd.read_csv('file.csv')
⦁ Excel: pd.read_excel('file.xlsx')
⦁ JSON: pd.read_json('file.json')
7. What is the difference between Python’s append() and extend() methods?
⦁ append() adds its argument as a single element to the end of a list.
⦁ extend() iterates over its argument adding each element to the list.
8. How do you filter rows in a Pandas DataFrame?
Using boolean indexing:
df[df['column'] > value] filters rows where ‘column’ is greater than value.
9. Explain the use of groupby() in Pandas with an example.
groupby() splits data into groups based on column(s), then you can apply aggregation.
Example: df.groupby('category')['sales'].sum() gives total sales per category.
10. What are lambda functions and how are they used?
Anonymous, inline functions defined with lambda keyword. Used for quick, throwaway functions without formally defining with def.
Example: df['new'] = df['col'].apply(lambda x: x*2)
React ♥️ for Part 2