Sql server® 2012 t-sql fundamentals

Self-Contained Subqueries

Every subquery has an outer query that it belongs to. Self-contained subqueries are subqueries that 

are independent of the outer query that they belong to. Self-contained subqueries are very conve-

nient to debug, because you can always highlight the subquery code, run it, and ensure that it does 

what it’s supposed to do. Logically, it’s as if the subquery code is evaluated only once before the outer 

query is evaluated, and then the outer query uses the result of the subquery. The following sections 

take a look at some concrete examples of self-contained subqueries.

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Microsoft SQL Server 2012 T-SQL Fundamentals