An EqualityComparer is not the way to go – it can only filter your result set in memory eg: var objects = yourResults.ToEnumerable().Distinct(yourEqualityComparer); You can use the GroupBy method to group by IDs and the First method to let your database only retrieve a unique entry per ID eg: var objects = yourResults.GroupBy(o => o.Id).Select(g … Read more
Try this: SELECT MIN(id) AS id, title FROM tbl_countries GROUP BY title
How about simply: select distinct c1, c2 from t or select c1, c2, count(*) from t group by c1, c2
To do a distinct on only one (or n) column(s): select distinct on (name) name, col1, col2 from names This will return any of the rows containing the name. If you want to control which of the rows will be returned you need to order: select distinct on (name) name, col1, col2 from names order … Read more
I assume that you use distinct like a method call on a list. You need to use the result of the query as datasource for your DropDownList, for example by materializing it via ToList. var distinctCategories = product .Select(m => new {m.CategoryId, m.CategoryName}) .Distinct() .ToList(); DropDownList1.DataSource = distinctCategories; DropDownList1.DataTextField = “CategoryName”; DropDownList1.DataValueField = “CategoryId”; Another … Read more
Notes.Select(x => x.Author).Distinct(); This will return a sequence (IEnumerable<string>) of Author values — one per unique value.
Here is one way to do it. Since you want the distinct counts as well, it can be done simply by grouping the rows twice. The first GROUP BY will remove duplicates, the second GROUP BY will produce the final result. WITH Sitings AS ( SELECT * FROM (VALUES (1, ‘Florida’, ‘Orlando’, ‘bird’), (2, ‘Florida’, … Read more
LINQ to Objects doesn’t provide this functionality easily in a built-in way, but MoreLINQ has a handy DistinctBy method: messages = messages.DistinctBy(m => new { m.id, m.date }).ToList();
The two queries express the same question. Apparently the query optimizer chooses two different execution plans. My guess would be that the distinct approach is executed like: Copy all business_key values to a temporary table Sort the temporary table Scan the temporary table, returning each item that is different from the one before it The … Read more
You’re looking for a group by: select * from table group by field1 Which can occasionally be written with a distinct on statement: select distinct on field1 * from table On most platforms, however, neither of the above will work because the behavior on the other columns is unspecified. (The first works in MySQL, if … Read more