CREATE TABLE table_203_657 (id NUMBER, "call sign" CLOB, "frequency" CLOB, "city of license" CLOB, "licensee" CLOB, "format" CLOB)

which cities have at least three call signs ?
SELECT "city of license" FROM table_203_657 GROUP BY "city of license" HAVING COUNT("call sign") >= 3
SELECT "city of license" FROM "table_203_657" GROUP BY "city of license" HAVING COUNT("call sign") >= 3