The summary.
THE STRUCTURE THAT MAKES EVERYTHING WORK
Raw data on one sheet, calculations on another, output on a third.
Data sheet: headers in row one, one record per row, no blank rows, no totals, no colour carrying meaning.
THE FEATURE TO LEARN FIRST
Pivot summaries. They turn a list of transactions into answers in seconds.
Revenue by month, by product, by customer — those three answer most basic questions.
THE THREE FUNCTIONS THAT ENABLE MOST ANALYSIS
Conditional sum, lookup, and extracting month or year from a date.
THE CHECK THAT CATCHES MOST ERRORS
Compare your total against the source system total. Always, before trusting anything else.
Then check the row count, and check the range each formula covers.
THE ERROR THAT DESTROYS DATA IRREVERSIBLY
Sorting one column without the others. Select everything, or use a table.
ON DATES
Text that looks like a date is not a date, and reformatting the display does not convert it.
Extract year and month into their own columns so you can group by period.
BEFORE SHARING ANY FILE
Check hidden rows, columns and sheets. They frequently contain more than intended.
