CREATE TABLE table_66478 ("City of license" TEXT, "Identifier" TEXT, "Frequency" TEXT, "Power" TEXT, "Class" TEXT, "RECNet" TEXT)

What identifier has 90.3 as the frequency?
SELECT "Identifier" FROM table_66478 WHERE "Frequency" = '90.3'
SELECT "Identifier" FROM "table_66478" WHERE "Frequency" = '90.3'