Writes and executes SQL queries from simple SELECTs to complex multi-table JOINs, aggregations, and subqueries. Use when the user asks to query a database, write SQL, run a SELECT statement, retrieve data, filter records, or generate reports from database tables.

Query Writing Skill Workflow for Simple Queries For straightforward questions about a single table: 1. Identify the table Which table has the data? 2. Get the schema Use sql db schema to see columns 3. Write the query SELECT relevant columns with WHERE/LIMIT/ORDER BY 4. Execute Run with sql db query 5. 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 Error Recovery If a query fails or returns unexpected results: 1. Empty results — Verify column names and WHERE conditions against the schema; check for case sensitivity or NULL values 2. Syntax error — Re examine JOINs, GROUP BY completeness, and alias references 3. 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)

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