CREATE TABLE "operating_system_support" (
  "client" text,
  "windows" text,
  "gnu_linux" text,
  "mac_os_x" text,
  "haiku" text
);

Question: Which Mac OSX's GNU/Linux was yes when Windows was no?
SQL: SELECT "mac_os_x" FROM "operating_system_support" WHERE "gnu_linux"='yes' AND "windows"='no';

Question: Which Mac OSX had no haiku and a client that was dc++?
SQL: SELECT "mac_os_x" FROM "operating_system_support" WHERE "haiku"='no' AND "client"='dc++';

Question: Which GNU/Linux had no haiku and a client of airdc++?
SQL: SELECT "gnu_linux" FROM "operating_system_support" WHERE "haiku"='no' AND "client"='airdc++';

Question: Which client had no GNU/Linux?
SQL: SELECT "client" FROM "operating_system_support" WHERE "gnu_linux"='no';