Step-by-step tutorials on Excel, Python, databases, and developer tools
132 articles
COUNTIFS returning zero even though matching rows clearly exist? The most common culprit is mismatched criteria range sizes. Here's exactly how to diagnose and fix it in under five minutes.
XLOOKUP's approximate match modes are more nuanced than VLOOKUP's. If your formula keeps returning #N/A even though the lookup value clearly exists in a nearby range, the match mode and sort order are almost certainly the culprits.
You created a GIN index on a JSONB column but EXPLAIN ANALYZE still shows a sequential scan. Here's why PostgreSQL ignores your index and the exact steps to fix it without rewriting your schema.
Your LATERAL JOIN looks correct, but it returns no rows — even though the outer table has data and the subquery runs fine in isolation. Here's why it silently fails and how to fix it.
PostgreSQL's UPDATE FROM syntax can silently update the wrong rows when a join matches multiple times — and you won't see an error. Here's how to diagnose, reproduce, and permanently fix this subtle bug in your queries.
Your INDEX MATCH formula looks right, but sorted data is feeding it wrong results. This guide breaks down the exact reason it happens and shows you the precise fix — no helper columns needed.
INDIRECT is powerful for dynamic references, but one wrong character in the sheet name and you get a #REF! error that's maddeningly hard to debug. Here's exactly what causes it and how to fix it for good.
Your SUMIFS formula looks right, but the total is off — and the culprit is almost always a wildcard you didn't place correctly or a data quirk Excel's pattern matcher handles unexpectedly. Here's how to diagnose and fix it.
Your SUMIFS formula looks right, but the moment you point a criteria range or criteria value at another sheet, it returns zero. Here's why that happens and exactly how to fix it.
TEXTJOIN returning an empty string when your range contains blank cells is one of Excel's more confusing silent failures. Here's exactly why it happens and how to fix it without restructuring your data.
Your COUNTIF formula looks right, but the count is off when you use wildcards. Learn exactly why asterisks and question marks mislead COUNTIF — and how to fix every common case.
Your SUMIFS total looks suspiciously high and you can't figure out why. Misaligned sum and criteria ranges are the most common culprit — and Excel won't warn you. Here's how to diagnose and fix it.