Exam PL-300 topic 1 question 6 discussion

Answer is correct

Answer is correct: 1. Inner join, 2. Left outer join If each row in table A has a matching row in table B, always use inner join because it has the best performance.

Answer is correct: 1. Inner Join - Because both table have matching rows 2. Left Outer - We can get all the matching and unmatching records from left table

The answer is correct: we need first an INNER JOIN between product and productSubcategory (in this way we will optimize since every product has a product subcategory) and we also need a left outer join between subcategory and category (left because not every product subcategory has a product category)

My biggest challenge with this specific question is paying attention the the clearly labeled headers vs. ignoring the order in which the tables were stated within the question itself.

How are you supposed to know that you shouldnt conserve all table information?

How you get product attribute from D option? is there right information you have in 2nd table regarding product?

Answer is correct. 1. Inner Join 2. Left Outer Join

A. Inner Join because we have only one row in Product for each ProductSubCategory. B. Left Join because we do not need rows from ProductCategory which do not match any ProductSubCategory

1: either Left outer or inner (same results) 2: left outer To fully understand this question, there are a few points: (1) Which to keep and which can be ignored. At the end of the day, we need to analyze the sales so all products need to be kept but unused subcategory and category can be ignored. (2) best performance : according to point1, we keep all products and ignore unused subcategories and categories. If it doesn't mention "best performance" and we want to keep all the subcategories and categories( which might be the case in real world cases),we can do full outer join on 3 tables. (3) left outer vs inner in question 1: As "Every Product has a ProductSubCategory", Let's say if there are subcategory 1,2,3 in product query and 1,2,3,4 in ProductSubCategory table, either left outer or inner join results in 1,2,3. (4) Let's say we have SubCategory 1,2 and we have Categories Sport,Drinks. SubCategory 1 is under Category Sport but Subcategory 2 is not under any Category. As we need to keep SubCategory 1,2, we need to do a Left outer join. If we keep Category Drinks then it defeats the purpose of "Best performance".

* The correct answer for the first option is Inner Join: it is because we want to keep only the rows where there's matching ProductSubCategory for each Product. * The correct answer for the second option is Left outer join: it is because not every ProductSubCategory has a parent ProductCategor, so we want to keep all ProductSubCategories while matching them with any available ProductCategories.

If I am building something from the client why would I take risk of missing out data from ProdSubCategory table in the Event say a new item in any table not present in other comes in? Answer is not practical for "Inner Join"

Please can somebody share source where it states Inner join better than Left join?

When Product and ProductSubCategory are merged, it will be still named as Product table. So second line should show Product, instead of ProductSubCategory. So confusing.

1. Inner 2. Left Outer

Answer is correct

Answer: - Inner join is the best option if you only want the matching rows from both tables. - Left outer join is useful if you want all the records from one of the tables. In this scenario, we want all the records from the "product subcategory" table, so we should use a left outer join.