![]() ![]() But as with the previous examples, Ecto’s querying DSL maps very closely to raw SQL, which makes it quite easy to use. It’s a little less elegant from Ecto’s perspective, since we can’t alias the average rating column - requiring us to use the same column calculation three times in the query. Let’s take a quick look at one of these returned records: Ecto’s Repo.all/2 function is then used to execute the query, where it fetches a list of results (since we expect more than one result from the query). Ecto provides a standardized API and a set of abstractions for talking to all the different kinds of databases, so that Elixir developers can query whatever database they're using by employing similar constructs. This works because Ecto will, by default, return all of the fields defined in the corresponding model’s schema definition if its select clause is omitted. As sql this would be the query: select c.id, c.name, (select count (s.id) from orderingsizes s where s.categoryid c. I want to count as a virtual column in the category the sizes total. To get the complete records for all users, we simply perform a query on the desired model (in this case, it’s Ectoing.User). ecto silviurosu March 29, 2017, 12:47pm 1 I have a schema category that has multiple sizes. select count(1) from (select distinct on(signature). (All examples will firstly show the SQL syntax, and then how this translates into the Ecto query syntax.) Alternatively, does Ecto have a way of nesting questies, so I could do. Let’s start with the most trivial of queries - selecting all users with their complete records: SELECT * FROM users query = Ectoing. This will make all of the querying DSL macros (such as from) available to us whilst working in the shell. And at the psql prompt I find it much easier to play with SQL. I’ll always see the solution in SQL first - translating to Ecto is an extra layer of indirection. Note that whilst all examples can be executed in the Elixir shell (via iex -S mix in the ectoing base directory), the Ecto.Query module will have to be imported first. After years of SQL, Ecto looks absolutely dyslexic to me and I know SQL way better than Ecto. SELECT c0."title", s1."record_count" FROM "cms_changelog_categories" AS c0 INNER JOIN (SELECT c0."category_id" AS "category_id", count(c0."id") AS "record_count" FROM "cms_changelog_records" AS c0 GROUP BY c0."category_id") AS s1 ON c0."id" = s1.Let’s start with some basic queries to get a feel for Ecto’s querying DSL. ![]() Like this : query = from p in ChangelogCategory,Ĭategory_version: c.cms_changelog_category_id, Where: p.seo_alias_link = ^category_alias_link,īut, didn’t work for me, I think to create 2 query to show things which I mean, don’t I?īy the way, I used category id relation in record instead of label name not its name !!! Join: c in assoc(p, :cms_changelog_record), def load_all_record_by_category(category_alias_link) do I need after counting and it shows me, now print all item in the category. (ecto) lib/ecto/repo/queryable.ex:133: /5 (ecto) lib/ecto/adapters/sql.ex:431: _and_cache/7 Let’s start with the most trivial of queries selecting all users with their complete records: SELECT FROM users query Ectoing.User query (All examples will firstly show. ![]() But I have an error : ** (Postgrex.Error) ERROR 42803 (grouping_error): column "c0.title" must appear in the GROUP BY clause or be used in an aggregate function ![]()
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