Data & Tools

Analysis starts with a tidy table: one row per thing, one column per fact, one value per cell. Most data problems are table problems.

• One header row with short, clear names (order_date, not 'Date of the order!!')
• One data type per column: all dates, all numbers or all text
• No merged cells, no blank rows, no totals mixed into the data
• Keep the raw file untouched and clean a copy

Ten formulas cover most of what a junior analyst does in a sheet.

=SUM(B2:B100)                 total
=AVERAGE(B2:B100)             mean
=COUNTA(A2:A100)              how many filled cells
=IF(B2>100, "big", "small")   a decision in a cell
=SUMIF(C:C, "Berlin", B:B)    total for one city
=COUNTIF(C:C, "Berlin")       how many in one city
=XLOOKUP(E2, A:A, B:B)        find a value in another table
=TRIM(A2)                     remove stray spaces
=ROUND(B2/C2, 2)              a rate to two decimals

SQL asks a database a question. The clauses always come in this order, and you can add only the ones you need.

SELECT city, COUNT(*) AS orders, SUM(total) AS revenue
FROM orders
WHERE order_date >= '2025-01-01'
GROUP BY city
HAVING SUM(total) > 100
ORDER BY revenue DESC
LIMIT 5;

• WHERE filters rows before grouping; HAVING filters groups after
• JOIN ... ON combines tables on a shared id
• Use aliases (AS) so results have readable names
• Test a query on a few rows with LIMIT before running it on everything

• Start bar charts at zero, or the differences look bigger than they are
• Title every chart with the finding, not just the topic
• Use one highlight colour and grey for the rest

You do not need all of these. Start with Sheets, one SQL tool and Looker Studio. Free options are enough to build a full portfolio.

• Clean a messy public spreadsheet and write down every change you made
• Answer five business questions about a small shop database with SQL
• Build a one-page Looker Studio dashboard from a Kaggle dataset
• Write a one-page case study: question, method, finding, recommendation
• Offer a free mini report to a local business and ask for feedback