![]() ![]() This requires some SQL like CREATE VIEW my_view AS followed by your query, which can be accessed with the name my_view. The first step is actually creating the view in the database. Wouldn’t it be great if Ecto could just treat streak data with the same elegant interface I can use with Habits and CheckIns? Happily, it can! Creating the View with a Migration With billions of results returned, there is probably not enough RAM in the world that can handle it. I have an Ecto query that is so big, that my machine cannot handle it. Awesome! Except that if I want to use this data in an Elixir function-perhaps to query the longest streak for habit-I have to copy and paste this big ball of SQL into an. Background PS: the following situation describes an hypothetical scenario, where I own a company that sells things to customers. +-+-+-įor every “streak”, it tells me which habit it belongs to (which makes it easy to query streaks for a given habit), when the streak started, ended, and how many days it lasted. ![]() Unfortunately, asking nicely looks like this: I only store habits and check-ins, but the database can figure out and tell us the streaks if we ask nicely. I don’t store “streaks” as a unique thing in the database. The intention-based on Jerry Seinfeld’s “don’t break the chain” motivational strategy-is that if I see that I’ve flossed 100 days in a row, I’m more likely to floss on the 101st. record that you’ve done it) once each day, and a streak is the number of days in a row that you’ve checked in. This work builds on 3264 which introduced the expr IN (subquery) syntax to Ecto.Query. In a side project of mine, an Elixir/Phoenix app for tracking daily habits called (imaginatively) Habits, the most complicated data logic involves figuring out “streaks” of check-ins. They provide a way to treat a complex query as if it were a simple table, and with no extra work, you can build Ecto schemas on top of database views to bring the power of that abstraction into your Elixir code! subset from (a in 'table1', where: a.id parameter, where: parentas (:table2).id in a.specialid1, a.specialid2, a.specialid3, select: 1) from (b in 'table2', as: :table2, where: exists (subquery (subset)), select: :firstname, :lastname) That should provide you the query you are looking for. But as with the previous examples, Ecto’s querying DSL maps very closely to raw SQL, which makes it quite easy to use.Database views are a great way to provide a simplified abstraction over complicated data logic. 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). 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. To get the complete records for all users, we simply perform a query on the desired model (in this case, it’s Ectoing.User). (All examples will firstly show the SQL syntax, and then how this translates into the Ecto query syntax.) 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. 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. Let’s start with some basic queries to get a feel for Ecto’s querying DSL. ![]()
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