Mysql 对组中的日期数据进行分页

我有一张这样的桌子：

create (DATETIME) |   Message (TEXT)
=========================================
2013-08-05 9:00:00  "Hi there!"
2013-08-05 10:00:00 "Hi again!"
2013-08-07 14:00:00 "Hi from the future!"

我希望能够在DATEcreate上获取所有消息和分组，以便按2013-08-05、2013-08-07等对消息进行分组。这可以通过以下方式轻松完成：

问题是我希望能够分组分页。例如，如果我有10个不同的日期，我想显示所有消息，每页5个日期组，并分页

我已经看到了很多限制组内元素数量的解决方案，但还没有看到任何限制组数量的解决方案

我基本上希望得到如下结果：

create (DATETIME) |   Message (TEXT)
=========================================
2013-08-05 9:00:00  "Hi there!"
2013-08-05 10:00:00 "Hi again!"
2013-08-07 14:00:00 "Hi from the future!"

如果限制为仅显示1组：

2013-08-05 9:00:00  "Hi there!"
2013-08-05 10:00:00 "Hi again!"

如果限制显示2组：

2013-08-05 9:00:00  "Hi there!"
2013-08-05 10:00:00 "Hi again!"
2013-08-07 14:00:00 "Hi from the future!"

如果限制显示跳过第一个组的1个组：

2013-08-07 14:00:00 "Hi from the future!"

---

如何在SQL中实现这一点？

我认为您需要计算组id并手动执行限制：

SELECT m.*
FROM messages m join
     (select date(create) as createdate, count(*) as cnt, @rn := @rn + 1 as groupnum
      from messages m cross join (select @rn := 0) const
      group by date(create)
     ) md
     on date(m.create) = createdate
WHERE groupnum between 1 and 5;

你可以这样做

仅限显示1组：

2013-08-05 9:00:00  "Hi there!"
2013-08-05 10:00:00 "Hi again!"

输出：

+---------------------+-----------+ | created | message | +---------------------+-----------+ | 2013-08-05 9:00:00 | Hi there! | | 2013-08-05 10:00:00 | Hi again! | +---------------------+-----------+ +---------------------+---------------------+ | created | message | +---------------------+---------------------+ | 2013-08-07 14:00:00 | Hi from the future! | +---------------------+---------------------+ 输出：

+---------------------+-----------+ | created | message | +---------------------+-----------+ | 2013-08-05 9:00:00 | Hi there! | | 2013-08-05 10:00:00 | Hi again! | +---------------------+-----------+ +---------------------+---------------------+ | created | message | +---------------------+---------------------+ | 2013-08-07 14:00:00 | Hi from the future! | +---------------------+---------------------+ 注意：确保在创建的列上有索引

---

下面是演示

示例数据更清晰：

查询1:从0开始的1组计数

SELECT m1.* FROM messages m1 JOIN (
  SELECT DISTINCT date(created) OnlyDate FROM messages
  ORDER BY OnlyDate
  LIMIT 0,1
) m2 ON date(m1.created) = OnlyDate;

|             CREATED |   MESSAGE |
|---------------------|-----------|
|  2013-08-05 9:00:00 | Hi there! |
| 2013-08-05 10:00:00 | Hi again! |

查询2:1组从1开始计数

SELECT m1.* FROM messages m1 JOIN (
  SELECT DISTINCT date(created) OnlyDate FROM messages
  ORDER BY OnlyDate
  LIMIT 1,1
) m2 ON date(m1.created) = OnlyDate

|             CREATED |             MESSAGE |
|---------------------|---------------------|
| 2013-08-07 14:00:00 | Hi from the future! |

您只需使用limit子句处理组，第一个值是起始组，第二个值是从它开始的偏移量。查询也应该相当有效，并且也不难阅读

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Fiddle.

我希望能够获得所有消息和组=>这是什么意思？您能提供您的预期输出吗？@MostyMostacho问题更新：