我整个下午都试图解决这个问题。我甚至不确定当前的数据库结构是否可行。我已经尝试了以下声明，但它没有返回我需要的内容。下面的语句的问题是它只返回projectType（如果存在）。如果projectType不存在，我需要返回零。非常感谢任何帮助。
SELECT r.region, ISNULL(o.totalcount,0) AS TotalCount, o.projectType
FROM region r
LEFT JOIN (
SELECT COUNT(o2.id) AS TotalCount, o2.regionID, t2.projectType
FROM projects o2
RIGHT JOIN projectTypes t2 on o2.typeID = t2.id
GROUP BY o2.regionId, t2.projectType
) o ON r.id = o.regionId
ORDER by r.Region
regions: ------------------------- id | region | ------------------------- 1 | East | ------------------------- 2 | MidWest | ------------------------- 3 | West | ------------------------- Project Type: ------------------------- id | projectType | ------------------------- 1 | Web Desgin | ------------------------- 2 | Database | ------------------------- 3 | Development | ------------------------- Projects: ------------------------------------------------------------------------- id | projectName | regionID | projectTypeID | postedOn | ------------------------------------------------------------------------- 1 | Project 1 | 1 | 2 | 2012-09-02 | ------------------------------------------------------------------------- 2 | Project 2 | 2 | 2 | 2012-09-02 | ------------------------------------------------------------------------- 3 | Project 3 | 1 | 1 | 2012-09-02 | ------------------------------------------------------------------------- 4 | Project 4 | 3 | 2 | 2012-09-02 | ------------------------------------------------------------------------- 5 | Project 5 | 3 | 1 | 2012-10-02 | ------------------------------------------------------------------------- 6 | Project 6 | 3 | 2 | 2012-10-02 | ------------------------------------------------------------------------- 7 | Project 7 | 3 | 3 | 2012-10-02 | ------------------------------------------------------------------------- 8 | Project 8 | 2 | 3 | 2012-10-02 | ------------------------------------------------------------------------- 9 | Project 9 | 1 | 2 | 2012-10-02 | ------------------------------------------------------------------------- 10 | Project 10 | 1 | 2 | 2012-10-02 | ------------------------------------------------------------------------- Desired Results: ----------------------------------------- Region | project Type | totalCount | ----------------------------------------- East | Web Desgin | 1 | ----------------------------------------- East | Database | 3 | ----------------------------------------- East | Development | 0 | ----------------------------------------- Midwest | Web Desgin | 0 | ----------------------------------------- Midwest | Database | 2 | ----------------------------------------- Midwest | Development | 1 | ----------------------------------------- West | Web Desgin | 1 | ----------------------------------------- West | Database | 2 | ----------------------------------------- West | Development | 1 | -----------------------------------------
答案 0 :(得分：4)
http://sqlfiddle.com/#!3/6680f/1
SELECT r.region
, pt.projectType
, count(p.id)
FROM region r cross join ProjectTypes pt
left join projects p on p.regionID = r.id and pt.id = p.TypeID
group by r.region, pt.projectType
order by r.region
答案 1 :(得分：1)
为什么不
SELECT regions.region, projectTypes.projectType,
(SELECT count(*) FROM projects
WHERE projects.typeID = projectTypes.id
AND projects.regionID = regions.id) as totalCount
FROM regions, projectTypes