Query Writing Skill

Workflow for Simple Queries

For straightforward questions about a single table:

• Identify the table - Which table has the data?

• Get the schema - Use sql_db_schema to see columns

• Write the query - SELECT relevant columns with WHERE/LIMIT/ORDER BY

• Execute - Run with sql_db_query

• Format answer - Present results clearly

Workflow for Complex Queries

For questions requiring multiple tables:

1. Plan Your Approach

Use write_todos to break down the task:

• Identify all tables needed

• Map relationships (foreign keys)

• Plan JOIN structure

• Determine aggregations

2. Examine Schemas

Use sql_db_schema for EACH table to find join columns and needed fields.

3. Construct Query

• SELECT - Columns and aggregates

• FROM/JOIN - Connect tables on FK = PK

• WHERE - Filters before aggregation

• GROUP BY - All non-aggregate columns

• ORDER BY - Sort meaningfully

• LIMIT - Default 5 rows

4. Validate and Execute

Check all JOINs have conditions, GROUP BY is correct, then run query.

Example: Revenue by Country

SELECT c.Country, ROUND(SUM(i.Total), 2) as TotalRevenue FROM Invoice i INNER JOIN Customer c ON i.CustomerId = c.CustomerId GROUP BY c.Country ORDER BY TotalRevenue DESC LIMIT 5;

Error Recovery

If a query fails or returns unexpected results:

• Empty results — Verify column names and WHERE conditions against the schema; check for case sensitivity or NULL values

• Syntax error — Re-examine JOINs, GROUP BY completeness, and alias references

• Timeout — Add stricter WHERE filters or LIMIT to reduce result set, then refine

Quality Guidelines

• Query only relevant columns (not SELECT *)

• Always apply LIMIT (5 default)

• Use table aliases for clarity

• For complex queries: use write_todos to plan

• Never use DML statements (INSERT, UPDATE, DELETE, DROP)