SELECT A.id,A.name,B.dep,C.class
FROM (test01 AS A LEFT JOIN test02 as B on A.id=B.id) LEFT JOIN test03 AS C on A.id=C.id
SQL Server：
SELECT A.id,A.name,B.dep,C.class
FROM test01 AS A LEFT OUTER JOIN test02 as B on A.id=B.id LEFT OUTER JOIN test03 AS C on A.id=C.id
Oracle：
SELECT A.id,A.name,B.dep,C.class
FROM test01 A,test02 B,test03 C
WHERE A.id=B.id(+) AND A.id=B.id(+)
或：
SELECT A.id,A.name,B.dep,C.class
FROM test01 A LEFT OUTER JOIN test02 B on (A.id=B.id) LEFT OUTER JOIN test03 C on (A.id=C.id)