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Learn T-SQL Querying
book

Learn T-SQL Querying

by Pedro Lopes, Pam Lahoud
May 2019
Intermediate to advanced content levelIntermediate to advanced
484 pages
11h 23m
English
Packt Publishing
Content preview from Learn T-SQL Querying

Using Common Table Expressions

Common Table Expressions (CTEs) are runtime constructs to derive an inline intermediate result set from a query. This means that a complex T-SQL query can be broken down into simpler T-SQL statements that store intermediate results before joining with other tables or other CTEs that had been previously defined in the T-SQL statement. For example, take the two following queries that can be executed in the AdventureWorks sample database:

WITH Sales_CTE(SalesPersonID, SalesOrderID, SalesYear)AS(  SELECT SalesPersonID, SalesOrderID, YEAR(OrderDate) AS SalesYear  FROM Sales.SalesOrderHeader  WHERE SalesPersonID IS NOT NULL)SELECT SalesPersonID, COUNT(SalesOrderID) AS TotalSales, SalesYearFROM Sales_CTEGROUP BY SalesYear, ...
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Publisher Resources

ISBN: 9781789348811Supplemental Content