Table: home_automation_systems
Columns: protocol
power_line
radio_frequency
open_source
needs_neutral_wire

Question: Does it need neutral wire when the power line and open source are no?
SQL: SELECT "needs_neutral_wire" FROM home_automation_systems 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 home_automation_systems 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 home_automation_systems WHERE "needs_neutral_wire" = 'no' AND "protocol" = 'x10'