CREATE TABLE "satellites_by_block" (
  "block" text,
  "launched" real,
  "operational" real,
  "not_usable" real,
  "retired" real,
  "launch_failures" real
);

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 "satellites_by_block" 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 "satellites_by_block" 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 "satellites_by_block" WHERE "retired"=0 AND "launch_failures"<1;