Division by zero 🗃️ SQL

SQL Error: division by zero / Divide by zero error encountered

An expression divided by a value that was 0 for at least one row.

Seen on: PostgreSQL MySQL SQL

Meaning

PostgreSQL and SQL Server raise an error; MySQL returns NULL (or errors in strict mode with ERROR_FOR_DIVISION_BY_ZERO). Ratios, averages and percentages over empty groups are the usual sources.

Common causes

  • Ratio with a zero denominator (no orders, no visits)
  • Average/percentage computed for empty groups
  • Data with unexpected zeros

⚡ Quick fix

  1. Wrap the denominator with NULLIF(x, 0)
  2. Use CASE to return 0 or NULL explicitly
  3. Filter out zero rows when they aren’t meaningful

Detailed fix by platform

SQL

  1. NULLIF guard:
    sql
    SELECT campaign, clicks * 100.0 / NULLIF(impressions, 0) AS ctr_percent
FROM campaign_stats;

How to diagnose

  1. Expression — Which division?
  2. Rows — Which rows have a 0 denominator?

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