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

Show names for all employees who do not have certificate of Boeing 737-800.
SELECT name FROM Employee EXCEPT 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 "name" FROM "Employee" EXCEPT 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"