SELECT DISTINCT 
a.Project_Yjdw as 移交单位, COUNT(a.Project_Id) AS 工程数量, SUM(a.Project_Mj) AS 面积, 
SUM(b.Docu_PageCount) AS 大图数量
FROM UDP_Project as a INNER JOIN
UDP_Document as b ON a.Project_Id = b.Docu_ForPro
GROUP BY a.Project_Id, a.Project_Yjdw, a.Project_Mj, b.Docu_PageCount

SELECT DISTINCT 
a.Project_Yjdw as 移交单位, COUNT(a.Project_Id) AS 工程数量, SUM(a.Project_Mj) AS 面积, 
SUM(b.Docu_PageCount) AS 大图数量
FROM UDP_Project as a INNER JOIN
UDP_Document as b ON a.Project_Id = b.Docu_ForPro
where b.Docu_PageCount＝2
GROUP BY a.Project_Id, a.Project_Yjdw, a.Project_Mj, b.Docu_PageCount

------解决方案--------------------
SQL code

SELECT DISTINCT 
a.Project_Yjdw as 移交单位, COUNT(a.Project_Id) AS 工程数量, SUM(a.Project_Mj) AS 面积, 
SUM(b.Docu_PageCount) AS 大图数量
FROM UDP_Project as a INNER JOIN
UDP_Document as b ON a.Project_Id = b.Docu_ForPro
GROUP BY a.Project_Id, a.Project_Yjdw, a.Project_Mj, b.Docu_PageCount
having b.Docu_PageCount＝2

------解决方案--------------------
那你先把子查询写出来，再把子查询当做表去关联

------解决方案--------------------
加個HAVING SUM(b.Docu_PageCount)=2

------解决方案--------------------
SQL code

--若是b.Docu_PageCount＝2,将其加在WHERE后
SELECT DISTINCT 
a.Project_Yjdw as 移交单位, COUNT(a.Project_Id) AS 工程数量, SUM(a.Project_Mj) AS 面积, 
SUM(b.Docu_PageCount) AS 大图数量
FROM UDP_Project as a INNER JOIN
UDP_Document as b ON a.Project_Id = b.Docu_ForPro
where b.Docu_PageCount＝2
GROUP BY a.Project_Id, a.Project_Yjdw, a.Project_Mj, b.Docu_PageCount

--若是sum(b.Docu_PageCount)＝2,将其加在having后
SELECT DISTINCT 
a.Project_Yjdw as 移交单位, COUNT(a.Project_Id) AS 工程数量, SUM(a.Project_Mj) AS 面积, 
SUM(b.Docu_PageCount) AS 大图数量
FROM UDP_Project as a INNER JOIN
UDP_Document as b ON a.Project_Id = b.Docu_ForPro
GROUP BY a.Project_Id, a.Project_Yjdw, a.Project_Mj, b.Docu_PageCount
having sum(b.Docu_PageCount)＝2