{"slug":"what-is-the-opening-auction","qid":"first_minute_vs_midday","label":"The 9:30 bar vs. the 12:30 bar: SPY, AAPL, NVDA on July 2, 2026","post_title":"What Is the Opening Auction? How Stocks Open","post_url":"/blog/what-is-the-opening-auction#q-first_minute_vs_midday","columns":["ticker","bar_0930_open","official_open","bar_open_minus_official_cents","bar_0930_vol_k","bar_0930_trades","bar_1230_vol_k","x_0930_vs_1230"],"rows":[{"ticker":"SPY","bar_0930_open":747.4,"official_open":747.22,"bar_open_minus_official_cents":18,"bar_0930_vol_k":479,"bar_0930_trades":8632,"bar_1230_vol_k":133,"x_0930_vs_1230":3.6},{"ticker":"AAPL","bar_0930_open":294.12,"official_open":294.1,"bar_open_minus_official_cents":2,"bar_0930_vol_k":743,"bar_0930_trades":14662,"bar_1230_vol_k":121,"x_0930_vs_1230":6.1},{"ticker":"NVDA","bar_0930_open":197.14,"official_open":197.12,"bar_open_minus_official_cents":2,"bar_0930_vol_k":1688,"bar_0930_trades":36319,"bar_1230_vol_k":226,"x_0930_vs_1230":7.5}],"shape":"table","sql":"WITH auctions AS (\n    SELECT ticker, toFloat64(argMax(price, (size, sip_timestamp))) AS official_open\n    FROM global_markets.stocks_trades\n    WHERE ticker IN ('SPY', 'AAPL', 'NVDA')\n      AND sip_timestamp >= '2026-07-02 00:00:00' AND sip_timestamp < '2026-07-03 00:00:00'\n      AND has(conditions, 17)\n    GROUP BY ticker\n)\nSELECT\n    b.ticker AS ticker,\n    toFloat64(anyIf(b.open, b.window_start = toDateTime('2026-07-02 09:30:00', 'America/New_York'))) AS bar_0930_open,\n    a.official_open AS official_open,\n    round(100 * (toFloat64(anyIf(b.open, b.window_start = toDateTime('2026-07-02 09:30:00', 'America/New_York'))) - a.official_open), 0) AS bar_open_minus_official_cents,\n    round(sumIf(b.volume, b.window_start = toDateTime('2026-07-02 09:30:00', 'America/New_York')) / 1e3) AS bar_0930_vol_k,\n    anyIf(b.transactions, b.window_start = toDateTime('2026-07-02 09:30:00', 'America/New_York')) AS bar_0930_trades,\n    round(sumIf(b.volume, b.window_start = toDateTime('2026-07-02 12:30:00', 'America/New_York')) / 1e3) AS bar_1230_vol_k,\n    round(sumIf(b.volume, b.window_start = toDateTime('2026-07-02 09:30:00', 'America/New_York')) / sumIf(b.volume, b.window_start = toDateTime('2026-07-02 12:30:00', 'America/New_York')), 1) AS x_0930_vs_1230\nFROM global_markets.delayed_stocks_minute_aggs AS b\nINNER JOIN auctions AS a ON a.ticker = b.ticker\nWHERE b.ticker IN ('SPY', 'AAPL', 'NVDA')\n  AND b.window_start >= toDateTime('2026-07-02 00:00:00', 'America/New_York')\n  AND b.window_start < toDateTime('2026-07-03 00:00:00', 'America/New_York')\nGROUP BY b.ticker, a.official_open\nORDER BY indexOf(['SPY', 'AAPL', 'NVDA'], b.ticker)","computed_at":"2026-07-26T06:24:35.938048+00:00","elapsed":1.135164938}