使用MySQL生成最近24小时整点时间临时表
作者：ps酷教程
MySQL临时表是一种只存在于当前数据库连接或会话期间的表,它们可以被用来存储临时数据,这些数据可以在查询中被使用,但是它们不会在数据库中永久存储,这篇文章主要给大家介绍了关于如何使用MySQL生成最近24小时整点时间临时表的相关资料,需要的朋友可以参考下
生成最近24小时整点
SELECT
-- 每向下推1行, @i比上次减去1
b.*, i.*,
DATE_FORMAT( DATE_SUB( NOW(), INTERVAL ( -( @i := @i - 1 ) ) HOUR ), '%Y-%m-%d %H:00' ) AS 'time'
FROM
-- 目的是生成12行数据
( SELECT
a
FROM
( SELECT '1' AS a UNION SELECT '2' UNION SELECT '3' UNION SELECT '4' ) AS a
JOIN ( SELECT '1' UNION SELECT '2' UNION SELECT '3' UNION SELECT '4' UNION SELECT '5' UNION SELECT '6' ) AS b ON 1
) AS b,
-- 先给1个默认的值
( SELECT @i := 1 ) AS i -- 每次跟主表连接1次, 都会动态计算列select中的值（就跟2张普通的表按条件连接起来,然后取表中的字段一样,只不过这里取的是@i,而@i属于会话变量而已）
-- ORDER BY time
生成最近30天
同理，往前推30天
SELECT DATE_FORMAT( DATE_SUB( NOW(), INTERVAL ( -( @i := @i - 1 ) ) DAY ), '%Y-%m-%d' ) AS 'time' FROM ( SELECT a FROM ( SELECT '1' AS a UNION SELECT '2' UNION SELECT '3' UNION SELECT '4' UNION SELECT '5' ) AS a JOIN ( SELECT '1' UNION SELECT '2' UNION SELECT '3' UNION SELECT '4' UNION SELECT '5' UNION SELECT '6' ) AS b ON 1 ) AS b, ( SELECT @i := 1 ) AS i ORDER BY time
生成最近12个月
SELECT DATE_FORMAT(CURDATE(), '%m') AS `month` UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 1 MONTH), '%m') AS `month` UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 2 MONTH), '%m') AS `month` UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 3 MONTH), '%m') AS `month` UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 4 MONTH), '%m') AS `month` UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 5 MONTH), '%m') AS `month` UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 6 MONTH), '%m') AS `month` UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 7 MONTH), '%m') AS `month` UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 8 MONTH), '%m') AS `month` UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 9 MONTH), '%m') AS `month` UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 10 MONTH), '%m') AS `month` UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 11 MONTH), '%m') AS `month`
总结
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