Table: crawley_data
Columns: number_on_map
name
colour
construction_commenced
population

Question: What is the average number for Northgate which commenced its construction before 1951?
SQL: SELECT AVG("number_on_map") FROM crawley_data WHERE "name" = 'northgate' AND "construction_commenced" < 1951

Question: What is the lowest population for the neighborhood with the color blue that commenced its construction before 1987?
SQL: SELECT MIN("population") FROM crawley_data WHERE "colour" = 'blue' AND "construction_commenced" < 1987