Spreadsheet how-to recipes

Common spreadsheet tasks with copy-paste formulas for Microsoft Excel, Google Sheets, and LibreOffice Calc — each one executed and verified in a real engine, not just documented.

• How to count the number of unique values in a range verified
• How to calculate the number of days between two dates verified
• How to get unique values (remove duplicates) with a formula verified
• How to join a list of cells into one comma-separated string verified
• How to look up a value with two criteria (multi-condition lookup) verified
• How to find the 2nd (or Nth) largest or smallest value verified
• How to calculate percentage change between two numbers verified
• How to sum values by category (conditional sum) with SUMIF verified
• How to VLOOKUP to the left (return a value from a column before the match) verified