再次求教大佬们 mysql 昨天的问题我勉强写出来了,但是有没有更好的方法呢 - V2EX
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再次求教大佬们 mysql 昨天的问题我勉强写出来了,但是有没有更好的方法呢

  •  
  •   chaodada 2020-02-04 09:51:01 +08:00 3683 次点击
    这是一个创建于 2151 天前的主题,其中的信息可能已经有所发展或是发生改变。

    select temp.* from ( SELECT COUNT(user_id) as count ,DATE_SUB(NOW(), INTERVAL 6 DAY) as count_time FROM test WHERE reg_time<DATE_SUB(NOW(), INTERVAL 6 DAY) UNION ALL SELECT COUNT(user_id) as count ,DATE_SUB(NOW(), INTERVAL 5 DAY) as count_time FROM test WHERE reg_time< DATE_SUB(NOW(), INTERVAL 5 DAY) UNION ALL SELECT COUNT(user_id) as count ,DATE_SUB(NOW(), INTERVAL 4 DAY) as count_time FROM test WHERE reg_time< DATE_SUB(NOW(), INTERVAL 4 DAY) UNION ALL SELECT COUNT(user_id) as count ,DATE_SUB(NOW(), INTERVAL 3 DAY) as count_time FROM test WHERE reg_time< DATE_SUB(NOW(), INTERVAL 3 DAY) UNION ALL SELECT COUNT(user_id) as count ,DATE_SUB(NOW(), INTERVAL 2 DAY) as count_time FROM test WHERE reg_time< DATE_SUB(NOW(), INTERVAL 2 DAY) UNION ALL SELECT COUNT(user_id) as count ,DATE_SUB(NOW(), INTERVAL 1 DAY) as count_time FROM test WHERE reg_time< DATE_SUB(NOW(), INTERVAL 1 DAY) UNION ALL SELECT COUNT(user_id) as count , DATE_SUB(NOW(), INTERVAL 0 DAY) as count_time FROM test WHERE reg_time< DATE_SUB(NOW(), INTERVAL 0 DAY) ) as temp

    求大佬们指教一下

    这是数据库 结构以及数据

    -- -- 数据库: test


    -- -- 表的结构 test

    CREATE TABLE test ( user_id int(11) NOT NULL, reg_time datetime NOT NULL ) ENGINE=MyISAM DEFAULT CHARSET=utf8;

    -- -- 转存表中的数据 test

    INSERT INTO test (user_id, reg_time) VALUES (1, '2020-01-21 08:08:08'), (2, '2020-01-22 00:00:00'), (3, '2020-01-23 08:08:08'), (4, '2020-01-24 08:08:08'), (5, '2020-01-25 08:08:08'), (6, '2020-01-26 08:08:08'), (7, '2020-01-27 08:08:08'), (8, '2020-01-28 00:00:00'), (9, '2020-01-29 09:09:09'), (10, '2020-01-30 13:08:08'), (11, '2020-01-31 15:08:05'), (12, '2020-02-01 17:08:08'), (13, '2020-02-02 21:00:00'), (14, '2020-02-03 05:08:09');

    -- -- 转储表的索引

    -- -- 表的索引 test

    ALTER TABLE test ADD PRIMARY KEY (user_id);

    -- -- 在导出的表使用 AUTO_INCREMENT

    -- -- 使用表 AUTO_INCREMENT test

    ALTER TABLE test MODIFY user_id int(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=15; COMMIT;

    4 条回复    2020-02-11 11:46:17 +08:00
    iyiluo
        1
    iyiluo  
       2020-02-04 10:23:42 +08:00
    先把大问题分解成小问题,sql 只做查询,不要在 sql 里面做太多计算,计算统一在应用里面。
    reg_time 为什么不直接传个日期过去,替换 DATE_SUB(...)?
    iyiluo
        2
    iyiluo  
       2020-02-04 10:26:51 +08:00
    @iyiluo 对了,如果不了解数据库引擎,大部分情况下用 Innodb 是没问题的,除非你有使用 MyISAM 的必要
    rekulas
        3
    rekulas  
       2020-02-04 13:29:17 +08:00
    多年使用 mysql 的经验是,复杂查询能将字段单独拉出来做索引表的就要拉出来,联合查询再怎么优化,也有瓶颈(确切的说比单独索引表差很多)
    lolizeppelin
        4
    lolizeppelin  
       2020-02-11 11:46:17 +08:00
    转 pg 解千愁
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