查询相关记录为0，这条数据就不显示了？
上次提问如何优化下面的SQL语句

SELECT   A.id,A.PrjTitle,
(
      SELECT   COUNT(B.ID)   FROM   Doc_Type   B   WHERE  
            (SELECT   COUNT(C.ID)   FROM   Doc_List   C   WHERE   C.Doctype   =   B.ID   AND   C.PrjID=A.ID)> 0
)   AS   TypeCount  
From   Doc_Project   A

得到很好的答案是：

SELECT   A.id,A.PrjTitle,COUNT(B.ID)  
FROM   Doc_Project   A,Doc_Type   B  
WHERE   EXISTS(SELECT   1   FROM   Doc_List   WHERE   Doctype   =   B.ID   AND   PrjID=A.ID)  
GROUP   BY   A.id,A.PrjTitle

但是测试发现优化后的SQL语句，   Doc_Project表的记录查询COUNT(B.ID)   如果为0就不显示此记录了，怎么能让查询为0也显示呢

------解决方案--------------------
left join
------解决方案--------------------
使用左外连接，left join / *=
------解决方案--------------------
try

SELECT A.id,A.PrjTitle,COUNT(B.ID)
FROM Doc_Project A left join Doc_Type B
ON EXISTS(SELECT 1 FROM Doc_List WHERE Doctype = B.ID AND PrjID=A.ID)
GROUP BY A.id,A.PrjTitle