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Code Quality

Querylab.io analyzes your SQL in real-time and highlights issues with colored underlines.

Severity Levels​

ColorSeverityMeaning
RedErrorQuery will fail — must fix
OrangeWarningCost/performance issue — should fix
BlueInfoPotential improvement
DottedHintOptional optimization

Hover over any underline to see details. Press Cmd+. (Mac) or Ctrl+. (Windows) for quick fixes.

Rules​

Cost & Performance​

  • SELECT * on large table
  • Large table scan without filters
  • Missing partition filter
  • Missing cluster filter
  • Wildcard table scan without filter
  • Wildcard table scan without _TABLE_SUFFIX (disabled)
  • ORDER BY without LIMIT
  • COUNT(DISTINCT) performance
  • Suboptimal clustering order

JOIN Issues​

  • CROSS JOIN detected
  • JOIN with OR condition
  • Missing JOIN condition
  • Ambiguous SELECT * with JOINs

NULL Handling​

  • NULL comparison with =

Column References​

  • Undefined column
  • Column references without FROM clause
  • Ambiguous column reference
  • Duplicate column/alias
  • Conflicting column and alias names
  • USING clause references non-existent column

GROUP BY & Aggregation​

  • Non-aggregated column in GROUP BY
  • HAVING without GROUP BY
  • Aggregate in WHERE clause
  • Nested aggregate functions
  • SELECT * with GROUP BY

Window Functions​

  • Window function in WHERE
  • QUALIFY without window function

CTEs​

  • Unused CTE
  • Duplicate CTE name
  • Undefined CTE references
  • CTE shadows table (disabled)

ORDER BY​

  • ORDER BY column not in SELECT
  • ORDER BY position out of range
  • LIMIT without ORDER BY in subquery

Type Consistency​

  • String in numeric comparison
  • CASE expression with inconsistent types

Subqueries​

  • Unnecessary subquery wrapping
  • Scalar subquery returning multiple columns
  • IN subquery returning multiple columns

Table & Alias References​

  • Undefined table alias
  • Duplicate table aliases
  • Invalid hierarchical naming (project.dataset.table)

Suggestions (lightbulb only)​

  • Suggest using QUALIFY clause
  • Suggest GROUP BY ALL
  • Suggest UNION BY NAME

Configuring Rules​

Settings → Diagnostic Rules to enable/disable specific rules.