Summary: Functions, Multiple Tables, and Sub-queries

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  • Tools for database management that offer built-in functions for performing operations on data within the database itself.

  • That when working with large datasets, you may save time by using built-in functions rather than first retrieving the data into your application and then executing functions on the retrieved data.

  • You can use sub-queries to form more powerful queries than otherwise.

  • You can use a sub-select expression to evaluate some built-in aggregate functions like the average function. 

  • Derived tables or table expressions are sub-queries where the outer query uses the results of the sub-query as a data source.


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