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Queries VIII: Dealing with ambiguous joins

Test yourself

Complete the following test so you can be sure you understand the material. Your answers are private, and test results are not scored.

You work around an ambiguous join by:

Reversing the direction of one of the joins.

Only querying tables that participate in a many-to-many relationship.

Querying the tables in one join, and then using that query as part of a second query that retrieves data from the other join.

An ambiguous outer join occurs when:

A base table participates in a left outer join.

The secondary table in an outer join participates in an additional join of any kind.

A secondary table serves as the data source for another query.

You build a query from another query when you need to:

Return only matching data from the base and secondary tables.

Return all the data from the base table and only matching data from the secondary table.

Break a complex query into smaller, more manageable pieces.

Bonus question: If you use only inner joins in structures like the ones discussed in this course, you don't have to worry about ambiguity errors.



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