| name | sql-analysis |
| description | Use this when writing, reviewing, or modifying SQL queries — including SELECT, CTEs, joins, aggregations, window functions, and validating query correctness or performance. |
Skill: SQL Analysis
Use this skill when writing, reviewing, or modifying SQL queries.
Rules
- Use explicit column names — avoid
SELECT * except for quick exploration.
- Use CTEs (Common Table Expressions) for readability and modularity.
- Add date filters for large fact tables to limit scan scope.
- Check join keys and join cardinality before writing joins.
- Validate row counts before and after joins to detect fanout or data loss.
- Avoid implicit cross joins.
- Never run
DROP, TRUNCATE, DELETE, or UPDATE unless explicitly requested by the user.
- If destructive SQL is requested, propose a dry-run, backup, or transaction strategy first.
Query Structure
WITH base AS (
SELECT
column_a,
column_b,
event_date
FROM schema.table_name
WHERE event_date BETWEEN '2024-01-01' AND '2024-01-31'
),
aggregated AS (
SELECT
column_a,
COUNT(*) AS row_count,
SUM(column_b) AS total_b
FROM base
GROUP BY column_a
)
SELECT
column_a,
row_count,
total_b
FROM aggregated
ORDER BY row_count DESC;
Review Checklist
Before finalizing a query, verify:
