SELECT 表A.numA, sun, moon, null star, conntent 
 FROM 表B,表A 
 WHERE 表B.numA = 表A.numA 
 UNION ALL 
 SELECT 表A.numA, sun,null moon, star, conntent 
 FROM 表C,表A 
 WHERE 表C.numA = 表A.numA 
 ORDER BY numA

 
 /*建表*/ 
 create table tableA 
 ( 
 numA varchar(10), 
 content varchar(10) 
 ) 
 create table tableB 
 ( 
 numA varchar(10), 
 sun varchar(10), 
 moon varchar(10) 
 ) 
 create table tableC 
 ( 
 numA varchar(10), 
 sun varchar(10), 
 star varchar(10) 
 ) 
  
 /*插值*/ 
 insert into tableA values ('黄','好人') 
 insert into tableA values ('刘','坏人') 
 insert into tableA values ('张','傻瓜') 
  
 insert into tableB values ('黄','很大','很小') 
 insert into tableB values ('黄','中间','一般大') 
 insert into tableB values ('刘','还好','微小') 
  
 insert into tableC values ('黄','很大','很小') 
 insert into tableC values ('张','中间','一般大') 
  
 /*查询*/ 
 select a.numA,b.sun,b.moon,c.star,a.content  
 from tableA a  
 left join tableB b on a.numA=b.numA   
 left join tableC c on a.numA=c.numA 
 

 
 CREATE TABLE  A 
 ( 
   numA varchar(10), 
   conntent  varchar(30) 
 ) 
 INSERT INTO A 
 SELECT '黄','好人' UNION ALL  
 SELECT '刘','坏人' UNION ALL  
 SELECT '张','傻瓜'  
  
  
 CREATE TABLE  B 
 ( 
   numA varchar(10), 
   sun varchar(10), 
   moon  varchar(30) 
 ) 
 INSERT INTO B 
 SELECT '黄','很大','很小' UNION ALL  
 SELECT '黄','中间','一般大' UNION ALL  
 SELECT '刘','还好','微小' 
  
  
 CREATE TABLE  C 
 ( 
   numA varchar(10), 
   sun varchar(10), 
   star  varchar(30) 
 ) 
  
 INSERT INTO C 
 SELECT '黄','很大','很小' UNION ALL  
 SELECT '张','中间','一般大'  
  
 select A.numA, C.sun, B.moon,C.star,A.conntent from A full join B on A.numA=B.numA 
   left join C on A.numA=C.numA 
 /* 
 numA     sun    moon               star               conntent