这将为您提供所需的服务。它不会对数据做任何假设，并且会提供所有丢失的记录。如果要将其限制为仅“ Switch 1”，则将其添加到WHERe子句中。
SELECt t1.Name, t1.VlanFROM t t1WHERe NOT EXISTS (SELECt 1 FROM t t2 WHERe t2.Name <> t1.Name AND t2.Vlan = t1.Vlan)CREATE TABLE t ( Name VARCHAr(10), Vlan INT)INSERT INTO t VALUES('Switch 1',1) INSERT INTO t VALUES('Switch 1', 2)INSERT INTO t VALUES('Switch 1', 3)INSERT INTO t VALUES('Switch 2', 1)INSERT INTO t VALUES('Switch 2', 2)
