W3Schools SQL | #28 SQL EXISTS 연산자

SQL EXISTS Operator

The SQL EXISTS Operator

하위 쿼리를 만족하는 레코드가 있는지 테스트
if랑 비슷한 역할
만약 하위 쿼리가 1개 이상의 레코드를 반환하는 경우
EXISTS 연산자는 TRUE를 반환한다 .

EXISTS Syntax

SELECT column_name(s)
FROM table_name
WHERE EXISTS
(SELECT column_name FROM table_name WHERE condition);

SQL EXISTS Examples

SELECT SupplierName
FROM Suppliers
WHERE EXISTS (SELECT ProductName FROM Products WHERE Products.SupplierID = Suppliers.supplierID AND Price < 20);

SELECT SupplierName
FROM suppliers
WHERE EXISTS (SELECT ProductName FROM Products WHERE Products.SupplierID = Suppliers.supplierID AND Price = 22);