EXISTS (Transact-SQL)
SQL Server 2005
Specifies a subquery to test for the existence of rows.
Transact-SQL Syntax Conventions
- subquery
-
Is a restricted SELECT statement. The COMPUTE clause, and the INTO keyword are not allowed. For more information, see the information about subqueries in SELECT (Transact-SQL).
A. Using NULL in a subquery to still return a result set
The following example returns a result set with NULL specified in the subquery and still evaluates to TRUE by using EXISTS.
USE AdventureWorks ; GO SELECT DepartmentID, Name FROM HumanResources.Department WHERE EXISTS (SELECT NULL) ORDER BY Name ASC ;
B. Comparing queries by using EXISTS and IN
The following example compares two queries that are semantically equivalent. The first query uses EXISTS and the second query uses IN.
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
The following query uses IN.
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
Here is the result set for either query.
FirstName LastName -------------------------------------------------- ---------- Barry Johnson David Johnson Willis Johnson (3 row(s) affected)
C. Comparing queries by using EXISTS and = ANY
The following example shows two queries to find stores whose name is the same name as a vendor. The first query uses EXISTS and the second uses = ANY.
USE AdventureWorks ; GO SELECT DISTINCT s.Name FROM Sales.Store s WHERE EXISTS (SELECT * FROM Purchasing.Vendor v WHERE s.Name = v.Name) ; GO
The following query uses = ANY.
USE AdventureWorks ; GO SELECT DISTINCT s.Name FROM Sales.Store s WHERE s.Name = ANY (SELECT v.Name FROM Purchasing.Vendor v ) ; GO
D. Comparing queries by using EXISTS and IN
The following example shows queries to find employees of departments that start with P.
USE AdventureWorks; GO SELECT c.FirstName, c.LastName, e.Title FROM Person.Contact c JOIN HumanResources.Employee e ON e.ContactID = c.ContactID WHERE EXISTS (SELECT * FROM HumanResources.Department d WHERE e.DepartmentID = d.DepartmentID AND d.Name LIKE 'P%'); GO
The following query uses IN.
USE AdventureWorks; GO SELECT c.FirstName, c.LastName, e.Title FROM Person.Contact c JOIN HumanResources.Employee e ON e.ContactID = c.ContactID WHERE DepartmentID IN (SELECT DepartmentID FROM HumanResources.Department WHERE Name LIKE 'P%'); GO
E. Using NOT EXISTS
NOT EXISTS works the opposite as EXISTS. The WHERE clause in NOT EXISTS is satisfied if no rows are returned by the subquery. The following example finds employees who are not in departments and have names that start with P.
USE AdventureWorks; GO SELECT c.FirstName, c.LastName, e.Title FROM Person.Contact c JOIN HumanResources.Employee e ON e.ContactID = c.ContactID WHERE NOT EXISTS (SELECT * FROM HumanResources.Department d WHERE e.DepartmentID = d.DepartmentID AND d.Name LIKE 'P%') ORDER BY LastName, FirstName GO
Here is the result set.
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)
Reference
Expressions (Transact-SQL)Functions (Transact-SQL)
WHERE (Transact-SQL)
