Table: deanie_hydroelectric_plant
Columns: name
year_commissioned
gross_head_metres
installed_capacity_megawatts
average_annual_output_million_kwh

Question: What is the earliest Year commissioned wiht an Average annual output greater than 58 and Installed capacity of 20?
SQL: SELECT MIN("year_commissioned") FROM deanie_hydroelectric_plant WHERE "average_annual_output_million_kwh" > 58 AND "installed_capacity_megawatts" = 20

Question: What is the Average annual output for Culligran power station with an Installed capacity less than 19?
SQL: SELECT AVG("average_annual_output_million_kwh") FROM deanie_hydroelectric_plant WHERE "name" = 'culligran' AND "installed_capacity_megawatts" < 19

Question: What is the Year Commissioned of the power stationo with a Gross head of less than 18?
SQL: SELECT AVG("year_commissioned") FROM deanie_hydroelectric_plant WHERE "gross_head_metres" < 18

Question: What is the Year commissioned of the power station with a Gross head of 60 metres and Average annual output of less than 59 million KWh?
SQL: SELECT MAX("year_commissioned") FROM deanie_hydroelectric_plant WHERE "gross_head_metres" = 60 AND "average_annual_output_million_kwh" < 59