Table: gps_satellites
Columns: block
launched
operational
not_usable
retired
launch_failures

Question: What is the total launch failures when there are 4 launches, and the not usable is greater than 0?
SQL: SELECT SUM("launch_failures") FROM gps_satellites WHERE "launched" = 4 AND "not_usable" > 0

Question: What is the highest number of not usable satellites when there are more than 0 launch failures, less than 30 retired, and the block is I?
SQL: SELECT MAX("not_usable") FROM gps_satellites WHERE "launch_failures" > 0 AND "retired" < 30 AND "block" = 'block i'

Question: What is the average number of not usable satellited when there are 0 retired, and the launch failures are less than 1?
SQL: SELECT AVG("not_usable") FROM gps_satellites WHERE "retired" = 0 AND "launch_failures" < 1