CREATE TABLE Employee (name VARCHAR, eid VARCHAR)
CREATE TABLE Aircraft (aid VARCHAR, name VARCHAR)
CREATE TABLE Certificate (eid VARCHAR, aid VARCHAR)

Show names for all employees who have certificate of Boeing 737-800.
SELECT T1.name FROM Employee AS T1 JOIN Certificate AS T2 ON T1.eid = T2.eid JOIN Aircraft AS T3 ON T3.aid = T2.aid WHERE T3.name = "Boeing 737-800"
SELECT "T1"."name" FROM "Employee" AS "T1" JOIN "Certificate" AS "T2" ON "T1"."eid" = "T2"."eid" JOIN "Aircraft" AS "T3" ON "Boeing 737-800" = "T3"."name" AND "T2"."aid" = "T3"."aid"