CREATE TABLE table_46741 ("Letter" CLOB, "IPv6 address" CLOB, "AS-number" CLOB, "Operator" CLOB, "Location #sites  ( global/local ) " CLOB, "Software" CLOB)

Which letter has an operator of the Defense Information Systems Agency?
SELECT "Letter" FROM table_46741 WHERE "Operator" = 'defense information systems agency'
SELECT "Letter" FROM "table_46741" WHERE "Operator" = 'defense information systems agency'