Drill Across generally use the following join to generate report:
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Self Join
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Inner Join
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Outter Join
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Both 1 & 2
Drill Across operations query multiple fact tables by joining them through conformed dimensions. Since different fact tables may not have matching rows for all dimension values, an Outer Join is required to preserve all data from both fact tables. Inner joins would lose unmatched records, and self-joins are used for hierarchical relationships within a single table.
To answer this question, let's go through each option to understand why it is correct or incorrect:
Option A) Self Join - This option is incorrect because a self join is used when a table is joined with itself, not when generating a report using Drill Across.
Option B) Inner Join - This option is incorrect because an inner join is used to select records that have matching values in both tables being joined. While it can be used in some cases to generate a report, it is not specifically used for Drill Across.
Option C) Outer Join - This option is correct because an outer join is used to select records from one table, even if there are no matching records in the other table. When generating a report using Drill Across, an outer join is often used to include all the records from one table and the matching records from the other table.
Option D) Both 1 & 2 - This option is incorrect because neither the self join nor the inner join is specifically used for Drill Across. Only the outer join is commonly used for this purpose.
The correct answer is C) Outer Join. This option is correct because an outer join is commonly used to generate a report using Drill Across, including all the records from one table and the matching records from the other table.