在公司项目中需要统计某月每天的所有数据,可以用一个辅助日历表实现,但是公司不允许建表,只有牺牲性能直接使用SQL语句来构建这个辅助表了。
SELECT ('2020-01-01' - INTERVAL DAY('2020-02-01') DAY) + INTERVAL s DAY AS days
FROM(
SELECT 31 AS s UNION ALL SELECT 30 UNION ALL SELECT 29
UNION ALL SELECT 28 UNION ALL SELECT 27 UNION ALL SELECT 26
UNION ALL SELECT 25 UNION ALL SELECT 24 UNION ALL SELECT 23
UNION ALL SELECT 22 UNION ALL SELECT 21 UNION ALL SELECT 20
UNION ALL SELECT 19 UNION ALL SELECT 18 UNION ALL SELECT 17
UNION ALL SELECT 16 UNION ALL SELECT 15 UNION ALL SELECT 14
UNION ALL SELECT 13 UNION ALL SELECT 12 UNION ALL SELECT 11
UNION ALL SELECT 10 UNION ALL SELECT 09 UNION ALL SELECT 08
UNION ALL SELECT 07 UNION ALL SELECT 06 UNION ALL SELECT 05
UNION ALL SELECT 04 UNION ALL SELECT 03 UNION ALL SELECT 02
UNION ALL SELECT 01) daytable
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