表格中的資料是時間戳格式，但我以日期（start_at）、日期（end_at）格式共享它。
表結構：
id, start_at, end_at
1, 03:00:00, 06:00:00
2, 02:00:00, 05:00:00
3, 01:00:00, 08:00:00
4, 08:00:00, 13:00:00
5, 09:00:00, 21:00:00
6, 13:00:00, 16:00:00
6, 15:00:00, 19:00:00
對于結果，我們需要計算在 start_at 和 end_at 時間之間處于活動狀態的 id。
hours, count
0, 0
1, 1
2, 2
3, 3
4, 3
5, 2
6, 1
7, 1
8, 1
9, 2
10, 2
11, 2
12, 2
13, 3
14, 2
15, 3
16, 2
17, 2
18, 2
19, 1
20, 1
21, 0
22, 0
23, 0
uj5u.com熱心網友回復：
任何一個
WITH RECURSIVE
cte AS (
SELECT 0 `hour`
UNION ALL
SELECT `hour` 1 FROM cte WHERE `hour` < 23
)
SELECT cte.`hour`, COUNT(test.id) `count`
FROM cte
LEFT JOIN test ON cte.`hour` >= HOUR(test.start_at)
AND cte.`hour` < HOUR(test.end_at)
GROUP BY 1
ORDER BY 1;
要么
WITH RECURSIVE
cte AS (
SELECT CAST('00:00:00' AS TIME) `hour`
UNION ALL
SELECT `hour` INTERVAL 1 HOUR FROM cte WHERE `hour` < '23:00:00'
)
SELECT cte.`hour`, COUNT(test.id) `count`
FROM cte
LEFT JOIN test ON cte.`hour` >= test.start_at
AND cte.`hour` < test.end_at
GROUP BY 1
ORDER BY 1;
第一個查詢以時間格式回傳小時列，而第二個查詢回傳此列的數值。選擇對您安全的變體。
https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=5a77b6e3158be06c7a551cb7e64673de
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