--- title: "WITH common_table_expression (Transact-SQL) | Microsoft Docs" ms.custom: "" ms.date: "08/09/2017" ms.prod: "sql-non-specified" ms.reviewer: "" ms.suite: "" ms.technology: - "database-engine" ms.tgt_pltfrm: "" ms.topic: "language-reference" f1_keywords: - "WITH common_table_expression" - "WITH_TSQL" - "WITH" - "common table expression" dev_langs: - "TSQL" helpviewer_keywords: - "WITH common_table_expression clause" - "CTEs" - "hierarchical queries [SQL Server], WITH common_table_expression" - "recursive CTEs [SQL Server]" - "recursive queries [SQL Server]" - "common table expressions" - "MAXRECURSION hint" - "clauses [SQL Server], WITH common_table_expression" ms.assetid: 27cfb819-3e8d-4274-8bbe-cbbe4d9c2e23 caps.latest.revision: 60 author: "BYHAM" ms.author: "rickbyh" manager: "jhubbard" --- # WITH common_table_expression (Transact-SQL) [!INCLUDE[tsql-appliesto-ss2008-all_md](../../includes/tsql-appliesto-ss2008-all-md.md)] Specifies a temporary named result set, known as a common table expression (CTE). This is derived from a simple query and defined within the execution scope of a single SELECT, INSERT, UPDATE, or DELETE statement. This clause can also be used in a CREATE VIEW statement as part of its defining SELECT statement. A common table expression can include references to itself. This is referred to as a recursive common table expression. ![Topic link icon](../../database-engine/configure-windows/media/topic-link.gif "Topic link icon") [Transact-SQL Syntax Conventions](../../t-sql/language-elements/transact-sql-syntax-conventions-transact-sql.md) ## Syntax ``` -- Syntax for SQL Server, Azure SQL Database, Azure SQL Data Warehouse, Parallel Data Warehouse [ WITH [ ,...n ] ] ::= expression_name [ ( column_name [ ,...n ] ) ] AS ( CTE_query_definition ) ``` ## Arguments *expression_name* Is a valid identifier for the common table expression. *expression_name* must be different from the name of any other common table expression defined in the same WITH \ clause, but *expression_name* can be the same as the name of a base table or view. Any reference to *expression_name* in the query uses the common table expression and not the base object. *column_name* Specifies a column name in the common table expression. Duplicate names within a single CTE definition are not allowed. The number of column names specified must match the number of columns in the result set of the *CTE_query_definition*. The list of column names is optional only if distinct names for all resulting columns are supplied in the query definition. *CTE_query_definition* Specifies a SELECT statement whose result set populates the common table expression. The SELECT statement for *CTE_query_definition* must meet the same requirements as for creating a view, except a CTE cannot define another CTE. For more information, see the Remarks section and [CREATE VIEW (Transact-SQL)](../../t-sql/statements/create-view-transact-sql.md). If more than one *CTE_query_definition* is defined, the query definitions must be joined by one of these set operators: UNION ALL, UNION, EXCEPT, or INTERSECT. ## Remarks ## Guidelines for Creating and Using Common Table Expressions The following guidelines apply to nonrecursive common table expressions. For guidelines that apply to recursive common table expressions, see "Guidelines for Defining and Using Recursive Common Table Expressions" that follows. - A CTE must be followed by a single SELECT, INSERT, UPDATE, or DELETE statement that references some or all the CTE columns. A CTE can also be specified in a CREATE VIEW statement as part of the defining SELECT statement of the view. - Multiple CTE query definitions can be defined in a nonrecursive CTE. The definitions must be combined by one of these set operators: UNION ALL, UNION, INTERSECT, or EXCEPT. - A CTE can reference itself and previously defined CTEs in the same WITH clause. Forward referencing is not allowed. - Specifying more than one WITH clause in a CTE is not allowed. For example, if a *CTE_query_definition* contains a subquery, that subquery cannot contain a nested WITH clause that defines another CTE. - The following clauses cannot be used in the *CTE_query_definition*: - ORDER BY (except when a TOP clause is specified) - INTO - OPTION clause with query hints - FOR BROWSE - When a CTE is used in a statement that is part of a batch, the statement before it must be followed by a semicolon. - A query referencing a CTE can be used to define a cursor. - Tables on remote servers can be referenced in the CTE. - When executing a CTE, any hints that reference a CTE may conflict with other hints that are discovered when the CTE accesses its underlying tables, in the same manner as hints that reference views in queries. When this occurs, the query returns an error. ## Guidelines for Defining and Using Recursive Common Table Expressions The following guidelines apply to defining a recursive common table expression: - The recursive CTE definition must contain at least two CTE query definitions, an anchor member and a recursive member. Multiple anchor members and recursive members can be defined; however, all anchor member query definitions must be put before the first recursive member definition. All CTE query definitions are anchor members unless they reference the CTE itself. - Anchor members must be combined by one of these set operators: UNION ALL, UNION, INTERSECT, or EXCEPT. UNION ALL is the only set operator allowed between the last anchor member and first recursive member, and when combining multiple recursive members. - The number of columns in the anchor and recursive members must be the same. - The data type of a column in the recursive member must be the same as the data type of the corresponding column in the anchor member. - The FROM clause of a recursive member must refer only one time to the CTE *expression_name*. - The following items are not allowed in the *CTE_query_definition* of a recursive member: - SELECT DISTINCT - GROUP BY - PIVOT (When the database compatibility level is 110 or higher. See [Breaking Changes to Database Engine Features in SQL Server 2016](../../database-engine/breaking-changes-to-database-engine-features-in-sql-server-2016.md).) - HAVING - Scalar aggregation - TOP - LEFT, RIGHT, OUTER JOIN (INNER JOIN is allowed) - Subqueries - A hint applied to a recursive reference to a CTE inside a *CTE_query_definition*. The following guidelines apply to using a recursive common table expression: - All columns returned by the recursive CTE are nullable regardless of the nullability of the columns returned by the participating SELECT statements. - An incorrectly composed recursive CTE may cause an infinite loop. For example, if the recursive member query definition returns the same values for both the parent and child columns, an infinite loop is created. To prevent an infinite loop, you can limit the number of recursion levels allowed for a particular statement by using the MAXRECURSION hint and a value between 0 and 32,767 in the OPTION clause of the INSERT, UPDATE, DELETE, or SELECT statement. This lets you control the execution of the statement until you resolve the code problem that is creating the loop. The server-wide default is 100. When 0 is specified, no limit is applied. Only one MAXRECURSION value can be specified per statement. For more information, see [Query Hints (Transact-SQL)](../../t-sql/queries/hints-transact-sql-query.md). - A view that contains a recursive common table expression cannot be used to update data. - Cursors may be defined on queries using CTEs. The CTE is the *select_statement* argument that defines the result set of the cursor. Only fast forward-only and static (snapshot) cursors are allowed for recursive CTEs. If another cursor type is specified in a recursive CTE, the cursor type is converted to static. - Tables on remote servers may be referenced in the CTE. If the remote server is referenced in the recursive member of the CTE, a spool is created for each remote table so the tables can be repeatedly accessed locally. If it is a CTE query, Index Spool/Lazy Spools is displayed in the query plan and will have the additional WITH STACK predicate. This is one way to confirm proper recursion. - Analytic and aggregate functions in the recursive part of the CTE are applied to the set for the current recursion level and not to the set for the CTE. Functions like ROW_NUMBER operate only on the subset of data passed to them by the current recursion level and not the entire set of data pased to the recursive part of the CTE. For more information, see example K. Using analytical functions in a recursive CTE that follows. ## Features and Limitations of Common Table Expressions in [!INCLUDE[ssSDW](../../includes/sssdw-md.md)] and [!INCLUDE[ssPDW](../../includes/sspdw-md.md)] The current implementation of CTEs in [!INCLUDE[ssSDW](../../includes/sssdw-md.md)] and [!INCLUDE[ssPDW](../../includes/sspdw-md.md)] have the following features and limitations: - A CTE can be specified in a **SELECT** statement. - A CTE can be specified in a **CREATE VIEW** statement. - A CTE can be specified in a **CREATE TABLE AS SELECT** (CTAS) statement. - A CTE can be specified in a **CREATE REMOTE TABLE AS SELECT** (CRTAS) statement. - A CTE can be specified in a **CREATE EXTERNAL TABLE AS SELECT** (CETAS) statement. - A remote table can be referenced from a CTE. - An external table can be referenced from a CTE. - Multiple CTE query definitions can be defined in a CTE. - A CTE must be followed by a single **SELECT** statement. **INSERT**, **UPDATE**, **DELETE**, and **MERGE** statements are not supported. - A common table expression that includes references to itself (a recursive common table expression) is not supported. - Specifying more than one **WITH** clause in a CTE is not allowed. For example, if a CTE_query_definition contains a subquery, that subquery cannot contain a nested **WITH** clause that defines another CTE. - An **ORDER BY** clause cannot be used in the CTE_query_definition, except when a **TOP** clause is specified. - When a CTE is used in a statement that is part of a batch, the statement before it must be followed by a semicolon. - When used in statements prepared by **sp_prepare**, CTEs will behave the same way as other **SELECT** statements in PDW. However, if CTEs are used as part of CETAS prepared by **sp_prepare**, the behavior can defer from [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] and other PDW statements because of the way binding is implemented for **sp_prepare**. If **SELECT** that references CTE is using a wrong column that does not exist in CTE, the **sp_prepare** will pass without detecting the error, but the error will be thrown during **sp_execute** instead. ## Examples ### A. Creating a simple common table expression The following example shows the total number of sales orders per year for each sales representative at [!INCLUDE[ssSampleDBCoFull](../../includes/sssampledbcofull-md.md)]. ``` -- Define the CTE expression name and column list. WITH Sales_CTE (SalesPersonID, SalesOrderID, SalesYear) AS -- Define the CTE query. ( SELECT SalesPersonID, SalesOrderID, YEAR(OrderDate) AS SalesYear FROM Sales.SalesOrderHeader WHERE SalesPersonID IS NOT NULL ) -- Define the outer query referencing the CTE name. SELECT SalesPersonID, COUNT(SalesOrderID) AS TotalSales, SalesYear FROM Sales_CTE GROUP BY SalesYear, SalesPersonID ORDER BY SalesPersonID, SalesYear; GO ``` ### B. Using a common table expression to limit counts and report averages The following example shows the average number of sales orders for all years for the sales representatives. ``` WITH Sales_CTE (SalesPersonID, NumberOfOrders) AS ( SELECT SalesPersonID, COUNT(*) FROM Sales.SalesOrderHeader WHERE SalesPersonID IS NOT NULL GROUP BY SalesPersonID ) SELECT AVG(NumberOfOrders) AS "Average Sales Per Person" FROM Sales_CTE; GO ``` ### C. Using multiple CTE definitions in a single query The following example shows how to define more than one CTE in a single query. Notice that a comma is used to separate the CTE query definitions. The FORMAT function, used to display the monetary amounts in a currency format, is available in SQL Server 2012 and higher. ``` WITH Sales_CTE (SalesPersonID, TotalSales, SalesYear) AS -- Define the first CTE query. ( SELECT SalesPersonID, SUM(TotalDue) AS TotalSales, YEAR(OrderDate) AS SalesYear FROM Sales.SalesOrderHeader WHERE SalesPersonID IS NOT NULL GROUP BY SalesPersonID, YEAR(OrderDate) ) , -- Use a comma to separate multiple CTE definitions. -- Define the second CTE query, which returns sales quota data by year for each sales person. Sales_Quota_CTE (BusinessEntityID, SalesQuota, SalesQuotaYear) AS ( SELECT BusinessEntityID, SUM(SalesQuota)AS SalesQuota, YEAR(QuotaDate) AS SalesQuotaYear FROM Sales.SalesPersonQuotaHistory GROUP BY BusinessEntityID, YEAR(QuotaDate) ) -- Define the outer query by referencing columns from both CTEs. SELECT SalesPersonID , SalesYear , FORMAT(TotalSales,'C','en-us') AS TotalSales , SalesQuotaYear , FORMAT (SalesQuota,'C','en-us') AS SalesQuota , FORMAT (TotalSales -SalesQuota, 'C','en-us') AS Amt_Above_or_Below_Quota FROM Sales_CTE JOIN Sales_Quota_CTE ON Sales_Quota_CTE.BusinessEntityID = Sales_CTE.SalesPersonID AND Sales_CTE.SalesYear = Sales_Quota_CTE.SalesQuotaYear ORDER BY SalesPersonID, SalesYear; GO ``` Here is a partial result set. ``` SalesPersonID SalesYear TotalSales SalesQuotaYear SalesQuota Amt_Above_or_Below_Quota ------------- --------- ----------- -------------- ---------- ---------------------------------- 274 2005 $32,567.92 2005 $35,000.00 ($2,432.08) 274 2006 $406,620.07 2006 $455,000.00 ($48,379.93) 274 2007 $515,622.91 2007 $544,000.00 ($28,377.09) 274 2008 $281,123.55 2008 $271,000.00 $10,123.55 ``` ### D. Using a recursive common table expression to display multiple levels of recursion The following example shows the hierarchical list of managers and the employees who report to them. The example begins by creating and populating the `dbo.MyEmployees` table. ``` -- Create an Employee table. CREATE TABLE dbo.MyEmployees ( EmployeeID smallint NOT NULL, FirstName nvarchar(30) NOT NULL, LastName nvarchar(40) NOT NULL, Title nvarchar(50) NOT NULL, DeptID smallint NOT NULL, ManagerID int NULL, CONSTRAINT PK_EmployeeID PRIMARY KEY CLUSTERED (EmployeeID ASC) ); -- Populate the table with values. INSERT INTO dbo.MyEmployees VALUES (1, N'Ken', N'Sánchez', N'Chief Executive Officer',16,NULL) ,(273, N'Brian', N'Welcker', N'Vice President of Sales',3,1) ,(274, N'Stephen', N'Jiang', N'North American Sales Manager',3,273) ,(275, N'Michael', N'Blythe', N'Sales Representative',3,274) ,(276, N'Linda', N'Mitchell', N'Sales Representative',3,274) ,(285, N'Syed', N'Abbas', N'Pacific Sales Manager',3,273) ,(286, N'Lynn', N'Tsoflias', N'Sales Representative',3,285) ,(16, N'David',N'Bradley', N'Marketing Manager', 4, 273) ,(23, N'Mary', N'Gibson', N'Marketing Specialist', 4, 16); ``` ``` USE AdventureWorks2012; GO WITH DirectReports(ManagerID, EmployeeID, Title, EmployeeLevel) AS ( SELECT ManagerID, EmployeeID, Title, 0 AS EmployeeLevel FROM dbo.MyEmployees WHERE ManagerID IS NULL UNION ALL SELECT e.ManagerID, e.EmployeeID, e.Title, EmployeeLevel + 1 FROM dbo.MyEmployees AS e INNER JOIN DirectReports AS d ON e.ManagerID = d.EmployeeID ) SELECT ManagerID, EmployeeID, Title, EmployeeLevel FROM DirectReports ORDER BY ManagerID; GO ``` ### E. Using a recursive common table expression to display two levels of recursion The following example shows managers and the employees reporting to them. The number of levels returned is limited to two. ``` USE AdventureWorks2012; GO WITH DirectReports(ManagerID, EmployeeID, Title, EmployeeLevel) AS ( SELECT ManagerID, EmployeeID, Title, 0 AS EmployeeLevel FROM dbo.MyEmployees WHERE ManagerID IS NULL UNION ALL SELECT e.ManagerID, e.EmployeeID, e.Title, EmployeeLevel + 1 FROM dbo.MyEmployees AS e INNER JOIN DirectReports AS d ON e.ManagerID = d.EmployeeID ) SELECT ManagerID, EmployeeID, Title, EmployeeLevel FROM DirectReports WHERE EmployeeLevel <= 2 ; GO ``` ### F. Using a recursive common table expression to display a hierarchical list The following example builds on Example D by adding the names of the manager and employees, and their respective titles. The hierarchy of managers and employees is additionally emphasized by indenting each level. ``` USE AdventureWorks2012; GO WITH DirectReports(Name, Title, EmployeeID, EmployeeLevel, Sort) AS (SELECT CONVERT(varchar(255), e.FirstName + ' ' + e.LastName), e.Title, e.EmployeeID, 1, CONVERT(varchar(255), e.FirstName + ' ' + e.LastName) FROM dbo.MyEmployees AS e WHERE e.ManagerID IS NULL UNION ALL SELECT CONVERT(varchar(255), REPLICATE ('| ' , EmployeeLevel) + e.FirstName + ' ' + e.LastName), e.Title, e.EmployeeID, EmployeeLevel + 1, CONVERT (varchar(255), RTRIM(Sort) + '| ' + FirstName + ' ' + LastName) FROM dbo.MyEmployees AS e JOIN DirectReports AS d ON e.ManagerID = d.EmployeeID ) SELECT EmployeeID, Name, Title, EmployeeLevel FROM DirectReports ORDER BY Sort; GO ``` ### G. Using MAXRECURSION to cancel a statement `MAXRECURSION` can be used to prevent a poorly formed recursive CTE from entering into an infinite loop. The following example intentionally creates an infinite loop and uses the `MAXRECURSION` hint to limit the number of recursion levels to two. ``` USE AdventureWorks2012; GO --Creates an infinite loop WITH cte (EmployeeID, ManagerID, Title) as ( SELECT EmployeeID, ManagerID, Title FROM dbo.MyEmployees WHERE ManagerID IS NOT NULL UNION ALL SELECT cte.EmployeeID, cte.ManagerID, cte.Title FROM cte JOIN dbo.MyEmployees AS e ON cte.ManagerID = e.EmployeeID ) --Uses MAXRECURSION to limit the recursive levels to 2 SELECT EmployeeID, ManagerID, Title FROM cte OPTION (MAXRECURSION 2); GO ``` After the coding error is corrected, MAXRECURSION is no longer required. The following example shows the corrected code. ``` USE AdventureWorks2012; GO WITH cte (EmployeeID, ManagerID, Title) AS ( SELECT EmployeeID, ManagerID, Title FROM dbo.MyEmployees WHERE ManagerID IS NOT NULL UNION ALL SELECT e.EmployeeID, e.ManagerID, e.Title FROM dbo.MyEmployees AS e JOIN cte ON e.ManagerID = cte.EmployeeID ) SELECT EmployeeID, ManagerID, Title FROM cte; GO ``` ### H. Using a common table expression to selectively step through a recursive relationship in a SELECT statement The following example shows the hierarchy of product assemblies and components that are required to build the bicycle for `ProductAssemblyID = 800`. ``` USE AdventureWorks2012; GO WITH Parts(AssemblyID, ComponentID, PerAssemblyQty, EndDate, ComponentLevel) AS ( SELECT b.ProductAssemblyID, b.ComponentID, b.PerAssemblyQty, b.EndDate, 0 AS ComponentLevel FROM Production.BillOfMaterials AS b WHERE b.ProductAssemblyID = 800 AND b.EndDate IS NULL UNION ALL SELECT bom.ProductAssemblyID, bom.ComponentID, p.PerAssemblyQty, bom.EndDate, ComponentLevel + 1 FROM Production.BillOfMaterials AS bom INNER JOIN Parts AS p ON bom.ProductAssemblyID = p.ComponentID AND bom.EndDate IS NULL ) SELECT AssemblyID, ComponentID, Name, PerAssemblyQty, EndDate, ComponentLevel FROM Parts AS p INNER JOIN Production.Product AS pr ON p.ComponentID = pr.ProductID ORDER BY ComponentLevel, AssemblyID, ComponentID; GO ``` ### I. Using a recursive CTE in an UPDATE statement The following example updates the `PerAssemblyQty` value for all parts that are used to build the product 'Road-550-W Yellow, 44' `(ProductAssemblyID``800`). The common table expression returns a hierarchical list of parts that are used to build `ProductAssemblyID 800` and the components that are used to create those parts, and so on. Only the rows returned by the common table expression are modified. ``` USE AdventureWorks2012; GO WITH Parts(AssemblyID, ComponentID, PerAssemblyQty, EndDate, ComponentLevel) AS ( SELECT b.ProductAssemblyID, b.ComponentID, b.PerAssemblyQty, b.EndDate, 0 AS ComponentLevel FROM Production.BillOfMaterials AS b WHERE b.ProductAssemblyID = 800 AND b.EndDate IS NULL UNION ALL SELECT bom.ProductAssemblyID, bom.ComponentID, p.PerAssemblyQty, bom.EndDate, ComponentLevel + 1 FROM Production.BillOfMaterials AS bom INNER JOIN Parts AS p ON bom.ProductAssemblyID = p.ComponentID AND bom.EndDate IS NULL ) UPDATE Production.BillOfMaterials SET PerAssemblyQty = c.PerAssemblyQty * 2 FROM Production.BillOfMaterials AS c JOIN Parts AS d ON c.ProductAssemblyID = d.AssemblyID WHERE d.ComponentLevel = 0; ``` ### J. Using multiple anchor and recursive members The following example uses multiple anchor and recursive members to return all the ancestors of a specified person. A table is created and values inserted to establish the family genealogy returned by the recursive CTE. ``` -- Genealogy table IF OBJECT_ID('dbo.Person','U') IS NOT NULL DROP TABLE dbo.Person; GO CREATE TABLE dbo.Person(ID int, Name varchar(30), Mother int, Father int); GO INSERT dbo.Person VALUES(1, 'Sue', NULL, NULL) ,(2, 'Ed', NULL, NULL) ,(3, 'Emma', 1, 2) ,(4, 'Jack', 1, 2) ,(5, 'Jane', NULL, NULL) ,(6, 'Bonnie', 5, 4) ,(7, 'Bill', 5, 4); GO -- Create the recursive CTE to find all of Bonnie's ancestors. WITH Generation (ID) AS ( -- First anchor member returns Bonnie's mother. SELECT Mother FROM dbo.Person WHERE Name = 'Bonnie' UNION -- Second anchor member returns Bonnie's father. SELECT Father FROM dbo.Person WHERE Name = 'Bonnie' UNION ALL -- First recursive member returns male ancestors of the previous generation. SELECT Person.Father FROM Generation, Person WHERE Generation.ID=Person.ID UNION ALL -- Second recursive member returns female ancestors of the previous generation. SELECT Person.Mother FROM Generation, dbo.Person WHERE Generation.ID=Person.ID ) SELECT Person.ID, Person.Name, Person.Mother, Person.Father FROM Generation, dbo.Person WHERE Generation.ID = Person.ID; GO ``` ### K. Using analytical functions in a recursive CTE The following example shows a pitfall that can occur when using an analytical or aggregate function in the recursive part of a CTE. ``` DECLARE @t1 TABLE (itmID int, itmIDComp int); INSERT @t1 VALUES (1,10), (2,10); DECLARE @t2 TABLE (itmID int, itmIDComp int); INSERT @t2 VALUES (3,10), (4,10); WITH vw AS ( SELECT itmIDComp, itmID FROM @t1 UNION ALL SELECT itmIDComp, itmID FROM @t2 ) ,r AS ( SELECT t.itmID AS itmIDComp , NULL AS itmID ,CAST(0 AS bigint) AS N ,1 AS Lvl FROM (SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4) AS t (itmID) UNION ALL SELECT t.itmIDComp , t.itmID , ROW_NUMBER() OVER(PARTITION BY t.itmIDComp ORDER BY t.itmIDComp, t.itmID) AS N , Lvl + 1 FROM r JOIN vw AS t ON t.itmID = r.itmIDComp ) SELECT Lvl, N FROM r; ``` The following results are the expected results for the query. ``` Lvl N 1 0 1 0 1 0 1 0 2 4 2 3 2 2 2 1 ``` The following results are the actual results for the query. ``` Lvl N 1 0 1 0 1 0 1 0 2 1 2 1 2 1 2 1 ``` `N` returns 1 for each pass of the recursive part of the CTE because only the subset of data for that recursion level is passed to `ROWNUMBER`. For each of the iterations of the recursive part of the query, only one row is passed to `ROWNUMBER`. ## Examples: [!INCLUDE[ssSDW](../../includes/sssdw-md.md)] and [!INCLUDE[ssPDW](../../includes/sspdw-md.md)] ### L. Creating a simple common table expression The following example shows the total number of sales orders per year for each sales representative at [!INCLUDE[ssSampleDBCoFull](../../includes/sssampledbcofull-md.md)]. ``` -- Uses AdventureWorks -- Define the CTE expression name and column list. WITH Sales_CTE (SalesPersonID, SalesOrderID, SalesYear) AS -- Define the CTE query. ( SELECT SalesPersonID, SalesOrderID, YEAR(OrderDate) AS SalesYear FROM Sales.SalesOrderHeader WHERE SalesPersonID IS NOT NULL ) -- Define the outer query referencing the CTE name. SELECT SalesPersonID, COUNT(SalesOrderID) AS TotalSales, SalesYear FROM Sales_CTE GROUP BY SalesYear, SalesPersonID ORDER BY SalesPersonID, SalesYear; GO ``` ### M. Using a common table expression to limit counts and report averages The following example shows the average number of sales orders for all years for the sales representatives. ``` WITH Sales_CTE (SalesPersonID, NumberOfOrders) AS ( SELECT SalesPersonID, COUNT(*) FROM Sales.SalesOrderHeader WHERE SalesPersonID IS NOT NULL GROUP BY SalesPersonID ) SELECT AVG(NumberOfOrders) AS "Average Sales Per Person" FROM Sales_CTE; GO ``` ### N. Using a common table expression within a CTAS statement The following example creates a new table containing the total number of sales orders per year for each sales representative at [!INCLUDE[ssSampleDBCoFull](../../includes/sssampledbcofull-md.md)]. ``` -- Uses AdventureWorks CREATE TABLE SalesOrdersPerYear WITH ( DISTRIBUTION = HASH(SalesPersonID) ) AS -- Define the CTE expression name and column list. WITH Sales_CTE (SalesPersonID, SalesOrderID, SalesYear) AS -- Define the CTE query. ( SELECT SalesPersonID, SalesOrderID, YEAR(OrderDate) AS SalesYear FROM Sales.SalesOrderHeader WHERE SalesPersonID IS NOT NULL ) -- Define the outer query referencing the CTE name. SELECT SalesPersonID, COUNT(SalesOrderID) AS TotalSales, SalesYear FROM Sales_CTE GROUP BY SalesYear, SalesPersonID ORDER BY SalesPersonID, SalesYear; GO ``` ### O. Using a common table expression within a CETAS statement The following example creates a new external table containing the total number of sales orders per year for each sales representative at [!INCLUDE[ssSampleDBCoFull](../../includes/sssampledbcofull-md.md)]. ``` -- Uses AdventureWorks CREATE EXTERNAL TABLE SalesOrdersPerYear WITH ( LOCATION = 'hdfs://xxx.xxx.xxx.xxx:5000/files/Customer', FORMAT_OPTIONS ( FIELD_TERMINATOR = '|' ) ) AS -- Define the CTE expression name and column list. WITH Sales_CTE (SalesPersonID, SalesOrderID, SalesYear) AS -- Define the CTE query. ( SELECT SalesPersonID, SalesOrderID, YEAR(OrderDate) AS SalesYear FROM Sales.SalesOrderHeader WHERE SalesPersonID IS NOT NULL ) -- Define the outer query referencing the CTE name. SELECT SalesPersonID, COUNT(SalesOrderID) AS TotalSales, SalesYear FROM Sales_CTE GROUP BY SalesYear, SalesPersonID ORDER BY SalesPersonID, SalesYear; GO ``` ### P. Using multiple comma separated CTEs in a statement The following example demonstrates including two CTEs in a single statement. The CTEs cannot be nested (no recursion). ``` WITH CountDate (TotalCount, TableName) AS ( SELECT COUNT(datekey), 'DimDate' FROM DimDate ) , CountCustomer (TotalAvg, TableName) AS ( SELECT COUNT(CustomerKey), 'DimCustomer' FROM DimCustomer ) SELECT TableName, TotalCount FROM CountDate UNION ALL SELECT TableName, TotalAvg FROM CountCustomer; ``` ## See Also [CREATE VIEW (Transact-SQL)](../../t-sql/statements/create-view-transact-sql.md) [DELETE (Transact-SQL)](../../t-sql/statements/delete-transact-sql.md) [EXCEPT and INTERSECT (Transact-SQL)](../../t-sql/language-elements/set-operators-except-and-intersect-transact-sql.md) [INSERT (Transact-SQL)](../../t-sql/statements/insert-transact-sql.md) [SELECT (Transact-SQL)](../../t-sql/queries/select-transact-sql.md) [UPDATE (Transact-SQL)](../../t-sql/queries/update-transact-sql.md)