获取行特定情况下的COUNT（）（计数将取决于列）

Question

我想获得行数，但“计数”是一个特定情况。

表A

   id   |  category  |         time
=============================================
      1 |          1 |  2015-02-09 12:00:00
      2 |          3 |  2015-02-09 13:00:00
      3 |          2 |  2015-02-09 14:00:00
      4 |          3 |  2015-02-09 14:00:00
      5 |          3 |  2015-02-09 15:00:00
      6 |          1 |  2015-02-09 16:00:00
      7 |          1 |  2015-02-09 16:00:00
      8 |          1 |  2015-02-09 17:00:00

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＆＃39;计数＆＃39;是相同的＆＃39;类别＆＃39;总数。

＆＃39;为了＆＃39;是“计数”的序数。按ASC排序

＆＃39;为了＆＃39;意思如下。

 order | counts | id | category |         time
========================================================
     1 |      4 |  1 |        1 |  2015-02-09 12:00:00
     2 |      4 |  6 |        1 |  2015-02-09 16:00:00
     3 |      4 |  7 |        1 |  2015-02-09 16:00:00
     4 |      4 |  8 |        1 |  2015-02-09 17:00:00

     1 |      1 |  3 |        2 |  2015-02-09 14:00:00

     1 |      3 |  2 |        3 |  2015-02-09 13:00:00
     2 |      3 |  4 |        3 |  2015-02-09 14:00:00
     3 |      3 |  5 |        3 |  2015-02-09 15:00:00

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如何编写查询以获得以下结果？ （添加两列）

结果

 order | counts | id | category |         time
========================================================
     1 |      4 |  1 |        1 |  2015-02-09 12:00:00
     1 |      3 |  2 |        3 |  2015-02-09 13:00:00
     1 |      1 |  3 |        2 |  2015-02-09 14:00:00
     2 |      3 |  4 |        3 |  2015-02-09 14:00:00
     3 |      3 |  5 |        3 |  2015-02-09 15:00:00
     2 |      4 |  6 |        1 |  2015-02-09 16:00:00
     3 |      4 |  7 |        1 |  2015-02-09 16:00:00
     4 |      4 |  8 |        1 |  2015-02-09 17:00:00

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Answer 1

使用以下

Select id,category,(select count(*) from catt as ct where ct.category = catt.category)as counts from catt

工作DEMO

根据第二项要求 - ＆gt;

set @category := '', @num := 1;


Select id,category,(select count(*) from catt as ct where ct.category = 

catt.category)as counts,@num := if(@category = catt.category, @num + 1, 1) as 

row_number , @category := category as dummy from catt order by category DESC

正在使用 SQLFiddle