tomevault-io Trino Query Skill
Critical Rules
- Read-only, NEVER run DDL/DML (
INSERT,UPDATE,DELETE,DROP,CREATE,ALTER) - Always LIMIT exploratory queries (start with
LIMIT 100) - Always use
--file, never--execute, for multi-line queries - Use Trino SQL dialect: uppercase keywords, double-quoted identifiers, ANSI syntax
Workflow
Write SQL to a file using Claude Write() and Edit() capabilities. Write to the
queries/tmpdirectory of a projectExecute the queries with:
trino --file queries/tmp/query_name.sqlInspect results, refine query, re-run if necessary
Run independent queries in parallel using background Bash tasks
Performance
- Avoid
SELECT COUNT(*) FROM tableon large tables - very slow without filters - Avoid
SELECT *- select only the columns you need - Always apply
WHEREfilters to narrow scans before aggregating - Use
LIMITfor exploratory queries - When filtering on partitioned columns (e.g.
year,month), include them inWHEREto enable partition pruning
Table Discovery
Use these commands to explore the database:
SHOW SCHEMAS FROM tq_production;
SHOW TABLES FROM tq_production.<schema>;
DESCRIBE tq_production.<schema>.<table>;
SHOW COLUMNS FROM tq_production.<schema>.<table>;
Error Handling
| Error | Fix |
|---|---|
COLUMN_NOT_FOUND |
Run SHOW COLUMNS FROM <table> to check exact column names |
TABLE_NOT_FOUND |
Run SHOW TABLES FROM <schema> to verify table exists |
Type mismatch (e.g. varchar vs integer) |
Use CAST(col AS type) to align types |
| Query timeout | Add WHERE filters, reduce scope, or add LIMIT |
SCHEMA_NOT_FOUND for payer data |
Check the year/month — use SHOW SCHEMAS FROM tq_production to find available months |
Available Tables
List of most important tables/schemas, not exhaustive. Only reference if necessary:
- Clear Rates (cleaned, validated price data): See references/clear-rates.md
- Hospital Price Transparency (hospital MRF price data): See references/hospital.md
- Payer Data (payer Transparency in Coverage price data): See references/payer.md
- Spines (reference data): See references/spines.md
- Claims Benchmarks (anonymized utilization, gross price data): See references/claims.md
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