Walk Through a Given SQL Query

At LSEG, a software engineer is reviewing a query that a teammate wrote to summarize the previous day's trading activity per instrument. The relevant tables are trades (trade_id, instrument_id, trade_ts, quantity, price, venue), instruments (instrument_id, symbol, currency), and corporate_actions (action_id, instrument_id, action_type, effective_date), where an instrument can have zero, one, or several corporate actions on record.

SELECT i.symbol,
       DATE(t.trade_ts) AS trade_date,
       SUM(t.quantity) AS total_volume,
       AVG(t.price) AS avg_price
FROM trades t
JOIN instruments i ON i.instrument_id = t.instrument_id
LEFT JOIN corporate_actions ca ON ca.instrument_id = t.instrument_id
WHERE t.trade_ts >= DATE '2026-10-07' - 1
GROUP BY i.symbol, DATE(t.trade_ts)
ORDER BY total_volume DESC;

Walk through what this query does, and explain how you would verify whether its output is actually correct.

Output

1. Return one row per instrument symbol and previous calendar date, with symbol, trade_date, total_volume, and avg_price.
2. Include only trades from the previous calendar day, exclude instruments without a matching instrument record, and order by total_volume descending.

Note: Treat DATE '2026-10-07' as today's date.