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Chapter 45. Joins > Understanding Joins

Understanding Joins

Data broken up across relational databases has all the advantages listed previously. It also has a disadvantage in that retrieving the data is more complex. To retrieve a list of customers with matching orders information, you might have to retrieve data from two tables. And to retrieve a list of employees with the department data, you might have to retrieve the information from three tables.

If you want to retrieve data from multiple tables (within a single operation, or with a single SELECT statement), the tables must be joined (and thus the term “joins”).


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