Median with PERCENTILE_CONT

-- Median order amount
SELECT PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY amount) AS median_amount
FROM   orders;

-- Latency percentiles (classic SLO query)
SELECT
  PERCENTILE_CONT(0.50) WITHIN GROUP (ORDER BY duration_ms) AS p50,
  PERCENTILE_CONT(0.90) WITHIN GROUP (ORDER BY duration_ms) AS p90,
  PERCENTILE_CONT(0.95) WITHIN GROUP (ORDER BY duration_ms) AS p95,
  PERCENTILE_CONT(0.99) WITHIN GROUP (ORDER BY duration_ms) AS p99
FROM   request_logs
WHERE  endpoint = '/api/users'
  AND  ts >= NOW() - INTERVAL '1 day';

-- Per-group percentiles
SELECT endpoint,
       PERCENTILE_CONT(0.95) WITHIN GROUP (ORDER BY duration_ms) AS p95
FROM   request_logs
GROUP  BY endpoint
ORDER  BY p95 DESC;