{"slug":"what-is-a-bid-ask-spread","qid":"intraday_checkpoints","label":"The same curve at four checkpoints: premarket, the open, midday, the close","post_title":"What Is a Bid-Ask Spread? Real Costs","post_url":"/blog/what-is-a-bid-ask-spread#q-intraday_checkpoints","columns":["et_time","median_spread_cents"],"rows":[{"et_time":"04:00","median_spread_cents":27},{"et_time":"09:30","median_spread_cents":4},{"et_time":"13:00","median_spread_cents":2},{"et_time":"16:00","median_spread_cents":10}],"shape":"series","sql":"SELECT formatDateTime(toStartOfInterval(toTimeZone(sip_timestamp, 'America/New_York'), INTERVAL 30 MINUTE), '%H:%i') AS et_time,\n       round(quantileDeterministic(0.5)(toFloat64(ask_price - bid_price), toUInt64(sip_timestamp)) * 100, 1) AS median_spread_cents\nFROM global_markets.cache_stocks_quotes\nWHERE ticker = 'AAPL'\n  AND sip_timestamp >= now() - INTERVAL 7 DAY\n  AND bid_price > 0\n  AND ask_price > bid_price\nGROUP BY et_time\nHAVING et_time IN ('04:00', '09:30', '13:00', '16:00')\nORDER BY et_time","computed_at":"2026-08-22T04:33:01.168777+00:00","elapsed":0.358965654}