MySQL如何获取按语句分组的行数

Question

I'm trying to get the count of the number of rows being grouped together in each of the result rows. For example:

SELECT * FROM table GROUP BY transid, other id on the following table

id      transid  other id
------------------------------
|1      |1        |1        |
|2      |1        |1        |
|3      |1        |1        |
|4      |1        |2        |
|5      |1        |2        |
|6      |1        |2        |
|7      |2        |1        |
|8      |2        |1        |
|9      |2        |2        |
|10     |3        |1        |
|11     |3        |1        |

RESULT:

 id      transid  other id
------------------------------
|1      |1        |1        |
|4      |1        |2        |
|7      |2        |1        |
|10     |2        |2        |
|11     |3        |1        |

How can I get:

 id      transid  other id   count
-------------------------------------
|1      |1        |1     |  3
|4      |1        |2     |  3
|7      |2        |1     |  2
|9      |2        |2     |  1
|10     |3        |1     |  2

Thank you.

Answer 1

Pick the min(id) of the grouped set and use count () to get the set count

Select min(id), transid, [other id], count(*) count
from table
Group by transid, [other id]

Answer 2

If all you're trying to do is count how many times there is a duplicate, you can simply do

Select Count(*), col1, col2 from tbl
group by col1, col2