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Where are Cartesian Joins used in real life?


By : Mugoya badru
Date : October 16 2020, 11:12 AM
will be helpful for those in need just random example. you have a table of cities: Id, Lat, Lon, Name. You want to show user table of distances from one city to another. You will write something like
code :


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Are all MySQL joins selections on the Cartesian product?


By : Maron San
Date : March 29 2020, 07:55 AM
should help you out Logically you are correct, joins are Cartesian products that are filtered; but practically the DBMS query processor is smarter than that.
You would need to look at a show plan or explain to see what it is doing under the covers.

SQL Inequality joins returning cartesian product


By : updz
Date : March 29 2020, 07:55 AM
I hope this helps . I have a problem getting join conditions to isolate unique records. My query is returning cartesian products, and I don't know how to make it stop. My tables look like this: , You want the following conditions to apply:
code :
    A.Start <= B.Time_1 <= B.Time_2 <= A.End
B.Time_2 <= A.End AND B.Time_1 >= A.Start
B.Time_1 <= A.End and B.Time_2 >= A.Start
B.Time_1 <= A.Start <= A.End <= B.Time_2
select A.*, B.Time_1, B.Time_2
from Table_A A
inner join
Table_B B
on 
A.ID_1 = B.ID_1 and B.Time_1>=A.Start and B.Time_2 <= A.End

Multiple Cartesian Joins pySpark


By : user2876984
Date : March 29 2020, 07:55 AM
Does that help I'm getting memory errors when doing multiple cartesian joins even though it's really small data sets. Can anyone explain why this would occur? , I ended up defining my own cartesianJoin function
code :
def cartesianJoin(self, other):
    return self.map(lambda rec: (0, rec)).join(other.map(lambda rec: (0, rec))).map(lambda (key, (x, y)): x.merge(y))
end

Can anybody help me to understand , Whats are the real life uses of redux in real-life scenario?


By : user3547974
Date : March 29 2020, 07:55 AM
may help you . If you use the same data, which needs to fetch in different screens(differenet components), so instead of fetch it every time better keep it in redux store. For example you have a list of orders, so this list can be useful in
Component, which shows list Component which shows statistic of orders Component which shows and allows to edit particular order

Avoiding Cartesian Product with Inner Joins


By : Thomas42
Date : March 29 2020, 07:55 AM
may help you . I used the example on this page : SQL query returning cartesian product to figure it out. In fairness I did not supply the database structure in my question. But the problem was that in each of the tables that I was joining there were more than one column that matched so I needed to reflect that in my Join statments. Here is a sample
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