Certified Data Analyst Associate Exam

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Question 25

Consider the following two statements:

Statement 1:

Statement 2:

Which of the following describes how the result sets will differ for each statement when they are run in Databricks SQL?

The first statement will return all data from the customers table and matching data from the orders table. The second statement will return all data from the orders table and matching data from the customers table. Any missing data will be filled in with NULL.

When the first statement is run, only rows from the customers table that have at least one match with the orders table on customer_id will be returned. When the second statement is run, only those rows in the customers table that do not have at least one match with the orders table on customer_id will be returned.

There is no difference between the result sets for both statements.

Both statements will fail because Databricks SQL does not support those join types.

When the first statement is run, all rows from the customers table will be returned and only the customer_id from the orders table will be returned. When the second statement is run, only those rows in the customers table that do not have at least one match with the orders table on customer_id will be returned.

Correct Answer: B

The first statement uses a LEFT SEMI JOIN, which will return all rows from the customers table that have at least one matching row in the orders table based on the customer_id. It does not return any columns from the orders table; it only checks for the existence of a match. The second statement uses a LEFT ANTI JOIN, which returns all rows from the customers table that do not have any matching row in the orders table based on the customer_id. Thus, the result sets for the two statements will differ, with the first query returning customers with orders and the second query returning customers without orders.

Discussion

MrWood47Option: B

Statement 1 uses a LEFT SEMI JOIN. This type of join returns all rows from the left table (customers) where there is at least one matching row in the right table (orders). It does not return any columns from the right table; it only checks for the existence of a match. Statement 2 uses a LEFT ANTI JOIN. This join returns all rows from the left table (customers) for which there is no matching row in the right table (orders). So, the result of Statement 1 will be all customer records that have made at least one order, and the result of Statement 2 will be all customer records that have not made any orders.

barmandOption: B

B is the correct Answer