EXISTS(Transact-SQL)
하위 쿼리를 지정하여 행의 존재 여부를 테스트합니다.
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구문
EXISTS subquery
인수
- subquery
제한된 SELECT 문입니다. COMPUTE 절과 INTO 키워드는 사용할 수 없습니다. 자세한 내용은 SELECT(Transact-SQL)에서 하위 쿼리에 대한 내용을 참조하십시오.
결과 유형
Boolean
결과 값
하위 쿼리에 행이 있으면 TRUE를 반환합니다.
예
1. 하위 쿼리에서 NULL을 사용하여 결과 집합 계속 반환
다음 예에서는 하위 쿼리에 NULL을 지정하여 결과 집합을 반환하고 EXISTS를 사용하여 TRUE로 계속 평가됩니다.
USE AdventureWorks ;
GO
SELECT DepartmentID, Name
FROM HumanResources.Department
WHERE EXISTS (SELECT NULL)
ORDER BY Name ASC ;
2. EXISTS 및 IN을 사용하여 쿼리 비교
다음 예에서는 기능이 동일한 두 쿼리를 비교합니다. 첫 번째 쿼리에서는 EXISTS를 사용하고 두 번째 쿼리에서는 IN을 사용합니다.
USE AdventureWorks ;
GO
SELECT a.FirstName, a.LastName
FROM Person.Contact AS a
WHERE EXISTS
(SELECT *
FROM HumanResources.Employee AS b
WHERE a.ContactId = b.ContactID
AND a.LastName = 'Johnson');
GO
다음 쿼리에서는 IN을 사용합니다.
USE AdventureWorks ;
GO
SELECT a.FirstName, a.LastName
FROM Person.Contact AS a
WHERE a.LastName IN
(SELECT a.LastName
FROM HumanResources.Employee AS b
WHERE a.ContactId = b.ContactID
AND a.LastName = 'Johnson');
GO
각 쿼리의 결과 집합은 다음과 같습니다.
FirstName LastName
-------------------------------------------------- ----------
Barry Johnson
David Johnson
Willis Johnson
(3 row(s) affected)
3. EXISTS 및 = ANY를 사용하여 쿼리 비교
다음 예에서는 공급업체와 이름이 동일한 상점을 찾는 두 개의 쿼리를 보여 줍니다. 첫 번째 쿼리에서는 EXISTS를 사용하고 두 번째 쿼리에서는 =ANY를 사용합니다.
USE AdventureWorks ;
GO
SELECT DISTINCT s.Name
FROM Sales.Store AS s
WHERE EXISTS
(SELECT *
FROM Purchasing.Vendor AS v
WHERE s.Name = v.Name) ;
GO
다음 쿼리에서는 = ANY를 사용합니다.
USE AdventureWorks ;
GO
SELECT DISTINCT s.Name
FROM Sales.Store AS s
WHERE s.Name = ANY
(SELECT v.Name
FROM Purchasing.Vendor AS v ) ;
GO
4. EXISTS 및 IN을 사용하여 쿼리 비교
다음 예에서는 P로 시작되는 부서의 직원을 찾는 쿼리를 보여 줍니다.
USE AdventureWorks;
GO
SELECT c.FirstName, c.LastName, e.Title
FROM Person.Contact AS c
JOIN HumanResources.Employee AS e
ON e.ContactID = c.ContactID
WHERE EXISTS
(SELECT *
FROM HumanResources.Department AS d
JOIN HumanResources.EmployeeDepartmentHistory AS edh
ON d.DepartmentID = edh.DepartmentID
WHERE e.EmployeeID = edh.EmployeeID
AND d.Name LIKE 'P%');
GO
다음 쿼리에서는 IN을 사용합니다.
USE AdventureWorks;
GO
SELECT c.FirstName, c.LastName, e.Title
FROM Person.Contact AS c JOIN HumanResources.Employee AS e
ON e.ContactID = c.ContactID
JOIN HumanResources.EmployeeDepartmentHistory AS edh
ON e.EmployeeID = edh.EmployeeID
WHERE edh.DepartmentID IN
(SELECT DepartmentID
FROM HumanResources.Department
WHERE Name LIKE 'P%');
GO
5. NOT EXISTS 사용
NOT EXISTS는 EXISTS와 반대됩니다. 하위 쿼리에서 반환되는 행이 없는 경우에는 NOT EXISTS의 WHERE 절 조건이 충족됩니다. 다음 예에서는 이름이 P로 시작되는 부서에 속하지 않는 직원을 찾습니다.
SELECT c.FirstName, c.LastName, e.Title
FROM Person.Contact AS c
JOIN HumanResources.Employee AS e
ON e.ContactID = c.ContactID
WHERE NOT EXISTS
(SELECT *
FROM HumanResources.Department AS d
JOIN HumanResources.EmployeeDepartmentHistory AS edh
ON d.DepartmentID = edh.DepartmentID
WHERE e.EmployeeID = edh.EmployeeID
AND d.Name LIKE 'P%')
ORDER BY LastName, FirstName
GO
결과 집합은 다음과 같습니다.
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
(91 row(s) affected)