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Exam PL-300 topic 2 question 87 discussion

Actual exam question from Microsoft's PL-300

Question #: 87
Topic #: 2

DRAG DROP
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You use Power Query Editor to import three tables named Customers, Address, and Country.

In the source system, not every customer has a related address, but every address has a related country.

You need to merge all the tables into a single query. The solution must optimize query refresh performance.

Which type of join should you use for each merge operation? To answer, drag the appropriate join types to the correct operations. Each join type may be used once, more than once, or not at all. You may need to drag the split bar between panes or scroll to view content.

NOTE: Each correct selection is worth one point.

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Suggested Answer:

by Endeetheanalyst at Sept. 5, 2024, 1:12 p.m.

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Endeetheanalyst

Highly Voted 11 months ago

This should be left outer join, since the customer table is on the left side.

upvoted 23 times

f534a80

7 months, 3 weeks ago

1. Should be left outer join 2. I don't understand the order of "join". If we join table customer+adress it would be still some customers with null values in adress therefore left outer join. If we join adress with country before joining customer with adress then should be inner join

upvoted 1 times

Rahultakle

7 months, 1 week ago

Use a Left Outer Join. This join will include all customers and their related addresses, if available. Since not every customer has an address, this join ensures that all customers are included, even if they don't have a corresponding address. Use an Inner Join. This join will include only the addresses that have a related country. Since every address has a related country, this join will ensure that all addresses are matched with their corresponding countries.

upvoted 1 times

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rcaliandro

Highly Voted 11 months ago

In my opinion it is wrong, it should be: Left outer, inner join

upvoted 14 times

rcaliandro

11 months ago

what do you think guys?

upvoted 1 times

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Lulu_2022

Most Recent 1 month ago

Customers → Address: Left Outer Join Not every customer has an address. A left outer join ensures all customers are retained, and only matching addresses are brought in. This avoids losing customers without addresses and keeps the dataset comprehensive. Address → Country: Inner Join Every address has a related country. An inner join is more efficient here because it only brings in matching country rows — and since all addresses have countries, no data is lost. This improves performance by reducing unnecessary rows.

upvoted 1 times

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Lulu_2022

1 month, 1 week ago

Merge: Customers → Address Join type: Left Outer Join Since not every customer has an address, you want to keep all customers and bring in address data only where it exists. A Left Outer Join ensures that all rows from Customers are retained, and matching rows from Address are added when available. 🔗 Merge: Address → Country Join type: Inner Join Because every address has a related country, you can safely use an Inner Join to bring in only matching rows. This is more efficient than a Left Join and helps optimize query performance.

upvoted 1 times

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2c7b65c

5 months ago

Understanding the Relationships: Customers ↔ Address Not every customer has an address → This means some customers may not be matched with an address. One-to-zero-or-one relationship → A customer may or may not have an address. Address ↔ Country Every address has a related country → This means all addresses will have a corresponding country. One-to-one relationship → Each address belongs to exactly one country. Query Plan: Merge Customers and Address using a Left Outer Join Retains all customers, even those without an address. Merge Address (now merged with Customers) and Country using an Inner Join Ensures that every address has a valid country.

upvoted 1 times

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SylUK

6 months, 1 week ago

The answer is Right outer and Inner: MY explanation for Right Outer; Customers is Left and Address Right , the question says 'not every Customer has a relalated Address ' this means in the source system, the Address table has all the records but the Customer table doesn't therefore the RIGHT OUTER should be perfect to merge both table according to the question explanations. Where we will obtain at the end ,a merge table with all addresses with their corresponding customer and even addresses without related customer(NULL VALUES). That means NOT EVERY CUSTOMER HAS A RELATED ADDRESS.

upvoted 2 times

santhosh28

5 months, 2 weeks ago

If you user right outer, any customer that has no address will not be part of the final table.

upvoted 1 times

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jaume

8 months, 2 weeks ago

to link customers with address we should use LEFT INNER to ensure we are getting all customers (from the left table) and matching addresses (every customer has a related address). Since LEFT INNER is not available, we should use the "opposite" which is RIGHT OUTER. Then, each address has a related country, we can use the INNER join

upvoted 1 times

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LuluSkyy

9 months, 3 weeks ago

I think the answer should be left outer since the customer table is on the left. so we should be all the records on the left table and the matching records on the right table.

upvoted 2 times

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VladStan

9 months, 4 weeks ago

Left outer, Inner

upvoted 1 times

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f07fa5c

10 months ago

Left outer, Inner

upvoted 1 times

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Jayaruwan

10 months, 3 weeks ago

My previous comment is wrong. I am sorry it is left outer and inner

upvoted 3 times

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Jayaruwan

10 months, 3 weeks ago

Right outer is correct because some customers have no address

upvoted 4 times

Arth_1111

10 months, 3 weeks ago

Left outer join is correct because we cant ignore the customers who does not have a address. Left table (Customers) should be included. 1. Left Outer Join 2. Inner Join

upvoted 6 times

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