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Se aplica a:
SQL ServerAzure SQL DatabaseAzure SQL Managed InstanceAzure Synapse AnalyticsAnalytics Platform System (PDW)Punto de conexión de análisis SQL en Microsoft FabricWarehouse en Microsoft FabricBase de datos SQL de Microsoft Fabric
Especifica una subconsulta para probar la existencia de filas.
Convenciones de sintaxis de Transact-SQL
Sintaxis
EXISTS ( subquery )
Argumentos
subconsulta
Una instrucción restringida SELECT . No se permite la INTO palabra clave . Para obtener más información, vea la información sobre las subconsultas en SELECT.
Tipos de retorno
Booleano
Valores de resultado
Devuelve TRUE si una subconsulta contiene filas.
Ejemplos
Los ejemplos de código de este artículo usan la base de datos de ejemplo de AdventureWorks2022 o AdventureWorksDW2022, que puede descargar de la página principal de Ejemplos de Microsoft SQL Server y proyectos de comunidad.
Un. Uso NULL en una subconsulta para devolver un conjunto de resultados
En el ejemplo siguiente se devuelve un conjunto de resultados con NULL especificado en la subconsulta TRUE y se sigue evaluando mediante EXISTS.
SELECT DepartmentID, Name
FROM HumanResources.Department
WHERE EXISTS (SELECT NULL)
ORDER BY Name ASC;
B. Comparación de consultas mediante EXISTS e IN
En el ejemplo siguiente se comparan dos consultas que son semánticamente equivalentes. En la primera consulta se utiliza EXISTS y en la segunda IN.
SELECT a.FirstName,
a.LastName
FROM Person.Person AS a
WHERE EXISTS (SELECT *
FROM HumanResources.Employee AS b
WHERE a.BusinessEntityID = b.BusinessEntityID
AND a.LastName = 'Johnson');
GO
En la siguiente consulta se usa IN.
SELECT a.FirstName,
a.LastName
FROM Person.Person AS a
WHERE a.LastName IN (SELECT a.LastName
FROM HumanResources.Employee AS b
WHERE a.BusinessEntityID = b.BusinessEntityID
AND a.LastName = 'Johnson');
GO
Este es el conjunto de resultados de cualquiera de las consultas.
FirstName LastName
-------------------------------------------------- ----------
Barry Johnson
David Johnson
Willis Johnson
C. Comparación de consultas mediante EXISTS y = ANY
En el ejemplo siguiente se muestran dos consultas para buscar tiendas cuyo nombre sea el mismo que el de un proveedor. En la primera consulta se usa EXISTS y en la segunda, = ANY.
SELECT DISTINCT s.Name
FROM Sales.Store AS s
WHERE EXISTS (SELECT *
FROM Purchasing.Vendor AS v
WHERE s.Name = v.Name);
GO
En la siguiente consulta se usa = ANY.
SELECT DISTINCT s.Name
FROM Sales.Store AS s
WHERE s.Name = ANY (SELECT v.Name
FROM Purchasing.Vendor AS v);
GO
D. Comparación de consultas mediante EXISTS e IN
En el siguiente ejemplo se muestran consultas para buscar empleados de departamentos que comiencen por P.
SELECT p.FirstName,
p.LastName,
e.JobTitle
FROM Person.Person AS p
INNER JOIN HumanResources.Employee AS e
ON e.BusinessEntityID = p.BusinessEntityID
WHERE EXISTS (SELECT *
FROM HumanResources.Department AS d
INNER JOIN HumanResources.EmployeeDepartmentHistory AS edh
ON d.DepartmentID = edh.DepartmentID
WHERE e.BusinessEntityID = edh.BusinessEntityID
AND d.Name LIKE 'P%');
GO
En la siguiente consulta se usa IN.
SELECT p.FirstName,
p.LastName,
e.JobTitle
FROM Person.Person AS p
INNER JOIN HumanResources.Employee AS e
ON e.BusinessEntityID = p.BusinessEntityID
INNER JOIN HumanResources.EmployeeDepartmentHistory AS edh
ON e.BusinessEntityID = edh.BusinessEntityID
WHERE edh.DepartmentID IN (SELECT DepartmentID
FROM HumanResources.Department
WHERE Name LIKE 'P%');
GO
E. Usar NOT EXISTS
NOT EXISTS funciona al contrario de EXISTS. La WHERE cláusula de NOT EXISTS se cumple si la subconsulta no devuelve ninguna fila. En el ejemplo siguiente se buscan empleados que no están en departamentos que tienen nombres que comienzan por P.
SELECT p.FirstName,
p.LastName,
e.JobTitle
FROM Person.Person AS p
INNER JOIN HumanResources.Employee AS e
ON e.BusinessEntityID = p.BusinessEntityID
WHERE NOT EXISTS (SELECT *
FROM HumanResources.Department AS d
INNER JOIN HumanResources.EmployeeDepartmentHistory AS edh
ON d.DepartmentID = edh.DepartmentID
WHERE e.BusinessEntityID = edh.BusinessEntityID
AND d.Name LIKE 'P%')
ORDER BY LastName, FirstName;
GO
Este es el conjunto de resultados.
FirstName LastName Title
------------------------------ ------------------------------ ------------
Syed Abbas Pacific Sales Manager
Hazem Abolrous Quality Assurance Manager
Humberto Acevedo Application Specialist
Pilar Ackerman Shipping & Receiving Superviso
François Ajenstat Database Administrator
Amy Alberts European Sales Manager
Sean Alexander Quality Assurance Technician
Pamela Ansman-Wolfe Sales Representative
Zainal Arifin Document Control Manager
David Barber Assistant to CFO
Paula Barreto de Mattos Human Resources Manager
Shai Bassli Facilities Manager
Wanida Benshoof Marketing Assistant
Karen Berg Application Specialist
Karen Berge Document Control Assistant
Andreas Berglund Quality Assurance Technician
Matthias Berndt Shipping & Receiving Clerk
Jo Berry Janitor
Jimmy Bischoff Stocker
Michael Blythe Sales Representative
David Bradley Marketing Manager
Kevin Brown Marketing Assistant
David Campbell Sales Representative
Jason Carlson Information Services Manager
Fernando Caro Sales Representative
Sean Chai Document Control Assistant
Sootha Charncherngkha Quality Assurance Technician
Hao Chen HR Administrative Assistant
Kevin Chrisulis Network Administrator
Pat Coleman Janitor
Stephanie Conroy Network Manager
Debra Core Application Specialist
Ovidiu Crãcium Sr. Tool Designer
Grant Culbertson HR Administrative Assistant
Mary Dempsey Marketing Assistant
Thierry D'Hers Tool Designer
Terri Duffy VP Engineering
Susan Eaton Stocker
Terry Eminhizer Marketing Specialist
Gail Erickson Design Engineer
Janice Galvin Tool Designer
Mary Gibson Marketing Specialist
Jossef Goldberg Design Engineer
Sariya Harnpadoungsataya Marketing Specialist
Mark Harrington Quality Assurance Technician
Magnus Hedlund Facilities Assistant
Shu Ito Sales Representative
Stephen Jiang North American Sales Manager
Willis Johnson Recruiter
Brannon Jones Finance Manager
Tengiz Kharatishvili Control Specialist
Christian Kleinerman Maintenance Supervisor
Vamsi Kuppa Shipping & Receiving Clerk
David Liu Accounts Manager
Vidur Luthra Recruiter
Stuart Macrae Janitor
Diane Margheim Research & Development Enginee
Mindy Martin Benefits Specialist
Gigi Matthew Research & Development Enginee
Tete Mensa-Annan Sales Representative
Ramesh Meyyappan Application Specialist
Dylan Miller Research & Development Manager
Linda Mitchell Sales Representative
Barbara Moreland Accountant
Laura Norman Chief Financial Officer
Chris Norred Control Specialist
Jae Pak Sales Representative
Wanda Parks Janitor
Deborah Poe Accounts Receivable Specialist
Kim Ralls Stocker
Tsvi Reiter Sales Representative
Sharon Salavaria Design Engineer
Ken Sanchez Chief Executive Officer
José Saraiva Sales Representative
Mike Seamans Accountant
Ashvini Sharma Network Administrator
Janet Sheperdigian Accounts Payable Specialist
Candy Spoon Accounts Receivable Specialist
Michael Sullivan Sr. Design Engineer
Dragan Tomic Accounts Payable Specialist
Lynn Tsoflias Sales Representative
Rachel Valdez Sales Representative
Garrett Vargar Sales Representative
Ranjit Varkey Chudukatil Sales Representative
Bryan Walton Accounts Receivable Specialist
Jian Shuo Wang Engineering Manager
Brian Welcker VP Sales
Jill Williams Marketing Specialist
Dan Wilson Database Administrator
John Wood Marketing Specialist
Peng Wu Quality Assurance Supervisor
Ejemplos: Azure Synapse Analytics y Sistema de la plataforma de análisis (PDW)
F. Uso de EXISTS
En el siguiente ejemplo se identifica si alguna fila de la tabla ProspectiveBuyer podría coincidir con alguna fila de la tabla DimCustomer. La consulta devuelve filas solo cuando coinciden los LastName valores y BirthDate de las dos tablas.
SELECT a.LastName, a.BirthDate
FROM DimCustomer AS a
WHERE EXISTS (SELECT *
FROM dbo.ProspectiveBuyer AS b
WHERE (a.LastName = b.LastName)
AND (a.BirthDate = b.BirthDate));
G. Usar NOT EXISTS
NOT EXISTS funciona como lo contrario que EXISTS. La WHERE cláusula de NOT EXISTS se cumple si la subconsulta no devuelve ninguna fila. En el ejemplo siguiente se buscan filas en la DimCustomer tabla donde y LastNameBirthDate no coinciden con ninguna entrada de la ProspectiveBuyers tabla.
SELECT a.LastName,
a.BirthDate
FROM DimCustomer AS a
WHERE NOT EXISTS (SELECT *
FROM dbo.ProspectiveBuyer AS b
WHERE (a.LastName = b.LastName)
AND (a.BirthDate = b.BirthDate));