Exam DA0-001 topic 1 question 47 discussion

A. Five rows, eight columns. Inner join returns only the rows where there is a match between the two tables in the specified join condition. In this case, the join condition would be based on the "Customer ID" column, which is present in both tables. So, the inner join of the two tables would result in 5 rows where there is a match in the "Customer ID" column, and each row would have 8 columns (all columns from both tables).

Table 1 has Customer_IDs: 004, 004, 008, 003, 001, 001, 002 Table 2 has Customer_IDs: 004, 009, 008, 003, 002, 001, 007 Let's count matches: 004 appears twice in Table 1, once in Table 2 = 2 rows in result 008 appears once in each = 1 row 003 appears once in each = 1 row 002 appears once in each = 1 row 001 appears twice in Table 1, once in Table 2 = 2 rows (009 and 007 only appear in Table 2, so they drop out) Total number of rows: 2 + 1 + 1 + 1 + 2 = 7 rows Count columns: Table 1: Customer_ID, Order_date, Product, Discount_code (4 columns) Table 2: Customer_ID, Active_flag, Segment, Store_ID, Spend (5 columns) When joined, Customer_ID appears only once Total columns: 4 + 5 - 1 = 8 columns Therefore, the result will have 7 rows and 8 columns.

B. I just tried in SQL

B is the correct answer. There are 7 rows in the order table, all those 7 rows will retain when inner join occurred because Customer_ID matches the customer table. Since customer like 001 and 004 appear twice in the order table, they will appear twice in the newly joined table as well. There are 8 columns because Customer_ID column is in both tables, 4 unique columns in customer table, 3 unique columns in order table, combined is 8 columns. I tried it with SQL and it returned 7 rows, A is not the answer, joined table can have duplicates.

B. Seven rows, eight columns