USING (fieldname) is a shorthand way of saying ON table1.fieldname = table2.fieldname. SQL doesn’t define the ‘order’ in which JOINS are done because it is not the nature of the language. Obviously an order has to be specified in the statement, but an INNER JOIN can be considered commutative: you can list them in any … Read more
Pretty good article on how it can be done: https://datarus.wordpress.com/2015/05/04/fighting-the-skew-in-spark/ Short version: Add random element to large RDD and create new join key with it Add random element to small RDD using explode/flatMap to increase number of entries and create new join key Join RDDs on new join key which will now be distributed better … Read more
There is no reason to ever use an implicit join (the one with the commas). Yes for inner joins it will return the same results. However, it is subject to inadvertent cross joins especially in complex queries and it is harder for maintenance because the left/right outer join syntax (deprecated in SQL Server, where it … Read more
I would suggest to avoid using default_scope, especially on something like price on another table. Every time you’ll use that table, join and ordering will take place, possibly giving strange results in complex queries and anyway making your query slower. There’s nothing wrong with a scope of its own, it’s simpler and it’s even clearer, … Read more
You have two options INNER JOIN x ON x.qid = y.qid OR (x.qid IS NULL AND y.qid IS NULL) or easier INNER JOIN x ON x.qid IS NOT DISTINCT FROM y.qid
I think what you are asking for will work by joining the Initial table to both Option_A and Option_B using LEFT JOIN, which will produce something like this: Initial LEFT JOIN Option_A LEFT JOIN NULL OR Initial LEFT JOIN NULL LEFT JOIN Option_B Example code: SELECT i.*, COALESCE(a.id, b.id) as Option_Id, COALESCE(a.name, b.name) as Option_Name … Read more
Try an OUTER APPLY SELECT C.Content_ID, C.Content_Title, C.Content_DatePublished, M.Media_Id FROM tbl_Contents C OUTER APPLY ( SELECT TOP 1 * FROM tbl_Media M WHERE M.Content_Id = C.Content_Id ) m ORDER BY C.Content_DatePublished ASC Alternatively, you could GROUP BY the results SELECT C.Content_ID, C.Content_Title, C.Content_DatePublished, M.Media_Id FROM tbl_Contents C LEFT OUTER JOIN tbl_Media M ON M.Content_Id = … Read more
You need to replace the second ON with AND, like this: ON a.userid = b.sourceid AND a.listid = b.destinationid;
I’m still not completely sure about your table relationships but from my guess, I came up with the following solution, first create the relationships using Eloquent models: User Model (for usres table): namespace App; use App\Course; use Illuminate\Notifications\Notifiable; use Illuminate\Foundation\Auth\User as Authenticatable; class User extends Authenticatable { use Notifiable; public function courses() { return $this->hasMany(Course::class); … Read more
.show() is a function with, what we call in Scala, a side-effect. It prints to stdout and returns Unit(), just like println Example: val a = Array(1,2,3).foreach(println) a: Unit = () In scala, you can assume that everything is a function and will return something. In your case, Unit() is being returned and that’s what’s … Read more