在多个表中递归的SQL Server查询

Question

我的表格结构如下,样本数据如下:名称:用户

User   Region
Sam    USA    
Meyer  NA    
Ying   Japan    
Yang   Asia

我还有另一张表,包括该地区和国家

名称:地区

       Region Country         RegionList    
        USA     America            
        NA       NULL          USA            
        NA      Canada            
        NA      Mexico            
        Japan   Japan
        Asia     NULL         Central        
        Asia      NULL         East        
        Central  India        
        East     Dubai
        Central  Japan

如何编写SQL服务器查询以列出他/她代表的每个用户和相应的国家/地区？

喜欢:

Sam   America
Meyer America
Meyer Canda
Meyer Mexico
Ying  Japan
Yang  Japan
Yang  India
Yang  Dubai

Answer 1

如果Region表可能具有无限多个级别,则可以使用公用表表达式.请参阅使用公用表表达式的递归查询.

WITH UserRegions (username, region, country)
AS
(
    -- Anchor member definition
    SELECT u.[user] AS username, r.regionlist AS region, r.country
    FROM [User] u
    JOIN Region r
        ON u.Region = r.Region
    UNION ALL
    -- Recursive member definition
    SELECT ur.username, r.regionlist AS region, r.country
    FROM Region r
    INNER JOIN UserRegions AS ur
        ON r.Region = ur.Region
)
-- Statement that executes the CTE
SELECT username, country
FROM UserRegions
WHERE country IS NOT NULL
ORDER BY username

http://sqlfiddle.com/#!3/ca9de/8