Error Handling And Debugging

---
name: sql-queries-error-handling-and-debugging
description: 'Sub-skill of sql-queries: Error Handling and Debugging.'
version: 1.0.0
category: data-analytics
type: reference
scripts_exempt: true
---

# Error Handling and Debugging

## Error Handling and Debugging


When a query fails:

1. **Syntax errors**: Check for dialect-specific syntax (e.g., `ILIKE` not available in BigQuery, `SAFE_DIVIDE` only in BigQuery)
2. **Column not found**: Verify column names against schema -- check for typos, case sensitivity (PostgreSQL is case-sensitive for quoted identifiers)
3. **Type mismatches**: Cast explicitly when comparing different types (`CAST(col AS DATE)`, `col::DATE`)
4. **Division by zero**: Use `NULLIF(denominator, 0)` or dialect-specific safe division
5. **Ambiguous columns**: Always qualify column names with table alias in JOINs
6. **Group by errors**: All non-aggregated columns must be in GROUP BY (except in BigQuery which allows grouping by alias)