2

如果城市中存在特定邻居，我想恢复一个布尔值

城市

City_Id | State_Id | CityName
1         6          São Paulo
2         22         São Paulo
3         26         São Paulo

邻居

Neighbor_Id | City_Id | NeighborName

询问

WITH cte
AS (
    SELECT City.*
    FROM City
    WHERE (City.CityName COLLATE SQL_Latin1_General_CP1_CI_AI) LIKE 'são paulo'
)
SELECT cte.*
    ,CASE 
    WHEN EXISTS (
            SELECT Neighbor.City_Id 
            FROM Neighbor
            INNER JOIN cte ON Neighbor.City_Id = cte.city_id
            WHERE (Neighbor.NeighborName COLLATE SQL_Latin1_General_CP1_CI_AI) LIKE 'ademar'
        )
        THEN 1
        ELSE 0
    END AS F
FROM cte

结果

City_Id | State_Id | CityName   | f
1         6          São Paulo    1
2         22         São Paulo    1
3         26         São Paulo    1

错误

我知道在 City_Id 2 中，我的表中不存在任何具有此城市 ID 的邻居，那么为什么CASE EXISTS在 City Id = 2 时在我的表中返回 1 ？

4

2 回答 2

2

您的问题正在发生，因为您在子查询中单独链接到 cte - 它不是针对主查询中特定行的 cte 检查邻居的值，而是针对整个cte。相反，请尝试将表达式更改为F：

CASE 
WHEN EXISTS (
        SELECT Neighbor.City_Id 
        FROM Neighbor
        WHERE Neighbor.City_Id = cte.city_id and
              (Neighbor.NeighborName COLLATE SQL_Latin1_General_CP1_CI_AI) LIKE 'ademar'
    )
    THEN 1
    ELSE 0
END AS F
于 2013-07-01T19:50:16.070 回答
1

为什么不进行实际测试 

WITH cte
AS (
    SELECT City.*
    FROM City
    WHERE (City.CityName COLLATE SQL_Latin1_General_CP1_CI_AI) LIKE 'são paulo'
)
            SELECT Neighbor.City_Id 
            FROM Neighbor
            INNER JOIN cte ON Neighbor.City_Id = cte.city_id
            WHERE (Neighbor.NeighborName COLLATE SQL_Latin1_General_CP1_CI_AI) LIKE 'ademar'
于 2013-07-01T19:24:12.460 回答