CREATE TABLE "comparison_of_popular_protocols" (
  "protocol" text,
  "power_line" text,
  "radio_frequency" text,
  "open_source" text,
  "needs_neutral_wire" text
);

Question: Does it need neutral wire when the power line and open source are no?
SQL: SELECT "needs_neutral_wire" FROM "comparison_of_popular_protocols" WHERE "power_line"='no' AND "open_source"='no';

Question: Does Zigbee need neutral wire when the open source is yes?
SQL: SELECT "needs_neutral_wire" FROM "comparison_of_popular_protocols" WHERE "open_source"='yes' AND "protocol"='zigbee';

Question: What's the open source of X10 that no neutral wire needed?
SQL: SELECT "open_source" FROM "comparison_of_popular_protocols" WHERE "needs_neutral_wire"='no' AND "protocol"='x10';