Advanced Query Techniques
Jonathan Eckstein, Bonnie R. Schultz · 2017
This chapter explores more advanced features of SQL. The reader is introduced to outer joins and how they can be useful within aggregation queries, along with various uses for the AS clause for creating table aliases. The chapter then describes the more complex query techniques of nested queries and query chaining. By feeding the result of one query into another query, query chaining can implement calculations that cannot be performed with a single SELECT statement. Nested queries are a similar technique in which one query may be embedded inside another. The chapter gives practical examples of both query chaining and nested queries.