Question

我的select语句最后有问题。我想要做的是选择两个级别，但我没有得到这个声明的结果。请注意，如果@Level为1，我不想小于1，否则可能会导致结果混乱，因此可能存在条件

它所在的部分@Level = @Level -1我遇到了

的问题

FROM c WHERE c.Level = @Level AND c.Level = @Level - 1 ORDER BY Level ASC

或者这个

FROM c WHERE c.Level BETWEEN @Level AND c.Level - 1 ORDER BY Level ASC

SQL

DECLARE @Department TABLE
(
Id INT NOT NULL,
Name varchar(50) NOT NULL,
ParentId int NULL
)

INSERT INTO @Department SELECT 1, 'Toys', null
INSERT INTO @Department SELECT 2, 'Computers', null,  
INSERT INTO @Department SELECT 3, 'Consoles', 2
INSERT INTO @Department SELECT 4, 'PlayStation 3', 3
INSERT INTO @Department SELECT 5, 'Xbox 360', 2
INSERT INTO @Department SELECT 6, 'Games', 1
INSERT INTO @Department SELECT 7, 'Puzzles', 6
INSERT INTO @Department SELECT 8, 'Mens Wear', null
INSERT INTO @Department SELECT 9, 'Mens Clothing', 8
INSERT INTO @Department SELECT 10, 'Jackets', 9
INSERT INTO @Department SELECT 11, 'Shoes', 9
INSERT INTO @Department SELECT 12, 'Rain Coats', 10

DECLARE  @Level int = 4
;WITH c AS
(
SELECT Id, ParentId, Name, 1 AS Level
FROM @Department
WHERE ParentId IS NULL

UNION ALL

SELECT t.Id, t.ParentId, T.Name, c.Level + 1 AS Level
FROM @Department T
INNER JOIN c on t.ParentId = c.Id   
)
SELECT Id, ParentId, Name, Level

FROM c WHERE c.Level = @Level AND c.Level = @Level - 1 ORDER BY Level ASC

FROM c WHERE c.Level BETWEEN @Level AND @Level - 1 ORDER BY Level ASC

Answer 1

也许FROM c WHERE c.Level BETWEEN @Level -1 AND @Level ORDER BY Level ASC

Answer 2

这里的代码从不能够工作：

@Level = @Level - 1

我想你想说：

c.Level = @Level - 1

即便如此......你可能想要OR而不是AND。

考虑一下你要问的内容......＆＃34;同时向我提供级别为4和5的所有记录。＆＃34;

你的意思可能是......＆＃34;给我所有水平为4或5的记录。＆＃34;

Answer 3

看看下面的SQL，它返回4行3级和1级4级：

SELECT p.Id as ParentId, 
    p.Name as Parent,
    c.Id, 
    c.Name, 
    c.Level
FROM c as c
left join c p 
on p.Id = c.ParentId
WHERE c.Level = @Level 
ORDER BY p.Name, c.Name ASC

Answer 4

好的，您的递归CTE似乎正确。我通常不会将name放在CTE中（主要是因为表只是父/子字段，或者有太多），然后加入，但它应该仍然可以正常工作。

正如已经指出的，你真正的问题是你的where条款是非感性的：

WHERE c.Level = @Level AND c.Level = @Level - 1基本上询问c.level == c.Level - 1 - 总是是否为假。
WHERE c.Level BETWEEN @Level AND @Level - 1要求@Level >= c.Level >= @Level - 1或@Level >= @Level - 1 - 另一个不可能的条件。

如果稍加修改，这些方法中的任何一种都应该可以正常工作：

WHERE c.Level = @Level OR c.Level = @Level - 1
WHERE c.Level BETWEEN @Level - 1 AND @Level

（@Level输入为1无关紧要 - 因为您开始为1，因此报告的级别没有更低级别。

select语句where子句的两个条件

4 个答案: