Does the answer lie within? Let’s find out. Joins are great, but sometimes you need to ask your database more than one question at a time. Or take the result of one query and use it as the input to another query. Introducing subqueries as the ultimate compartmentalization tool. Subqueries help you avoid duplicate data, make your queries more dynamic, and even help you score tickets to that sold-out K-pop concert. (Well, not really, but two out of three ain’t bad!) You’ll soon discover how versatile subqueries can be, returning single values, columns, or even tabular results when serving as a derived table. And you’ll learn more about choosing between alternate SQL syntax options like subqueries, joins, or common table expressions (CTEs). It’s all embedded in this chapter, so head inwards for more.
Low-budget options
Abby has been following along and thinks those joins and unions are pretty slick. She’s considering the relationships between her tables and has set up her tables and keys nicely. But remember, Abby’s travel_db database isn’t just for SQL learning. She needs to use it to plan out upcoming trips.
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