CREATE TABLE "captain" (
"Captain_ID" int,
"Name" text,
"Ship_ID" int,
"age" text,
"Class" text,
"Rank" text,
PRIMARY KEY ("Captain_ID"),
FOREIGN KEY ("Ship_ID") REFERENCES "Ship"("Ship_ID")
)

CREATE TABLE "Ship" (
"Ship_ID" int,
"Name" text,
"Type" text,
"Built_Year" real,
"Class" text,
"Flag" text,
PRIMARY KEY ("Ship_ID")
)
SELECT count(*) ,  rank FROM captain WHERE age  <  50 GROUP BY rank
Count the number of captains younger than 50 of each rank.