True or False: The best way to determine whether an inner join or a left outer join should be used is the starting table's primary key.

True or False: The best way to determine whether an inner join or a left outer join should be used is the starting table's primary key.

• A. True
• B. False; the reporting need, load type and frequency will determine whether two tables should be joined using a left outer join or an inner join.
• C. True; but only for inner join
• D. False; determined by the size of the dataset

Answer: (B)

False. The choice between an inner join and a left outer join hinges on the result you need, not on the starting table’s primary key. An inner join returns only rows with matching data in both tables, which is what you want when you need corresponded records in every row. A left outer join keeps every row from the left table, even if there’s no matching row on the right, filling in gaps with nulls. The primary key on the starting table just defines unique identity; it doesn’t tell you whether you should include non-matching rows or how to handle missing matches. So you decide based on reporting needs and data-loading goals: for reports that require all items from the left side, use a left join; for reports that require only matched pairs, use an inner join. Size of the dataset is not the determining factor.

False. The choice between an inner join and a left outer join hinges on the result you need, not on the starting table’s primary key. An inner join returns only rows with matching data in both tables, which is what you want when you need corresponded records in every row. A left outer join keeps every row from the left table, even if there’s no matching row on the right, filling in gaps with nulls. The primary key on the starting table just defines unique identity; it doesn’t tell you whether you should include non-matching rows or how to handle missing matches. So you decide based on reporting needs and data-loading goals: for reports that require all items from the left side, use a left join; for reports that require only matched pairs, use an inner join. Size of the dataset is not the determining factor.