选择每个用户和日期仅一行

Question

i want to select only one row per user and date

so if the data like this

ID  User    Date
25  3597    2014-09-04 13:37:12.953
26  2100    2014-09-04 13:37:29.820
27  3597    2014-09-04 13:38:12.953
28  2100    2014-09-04 13:38:29.820
29  3597    2014-09-05 13:40:12.953
30  2100    2014-09-05 13:40:29.820

the result should be 4

Answer 1

The result should be 4

If all you need is the count, in SQL, you can use COUNT(DISTINCT) , like this:

SELECT COUNT(DISTINCT User, Date) FROM MyTable

In LINQ, you can use GroupBy followed by Count :

int cnt = src.Items.GroupBy(item => new {i.User, i.Date}).Count();