[英]How can we write a recursive SQL query in T-SQL?
我們如何在 T-SQL 中編寫遞歸 SQL 查詢?
你能舉一個簡單的例子來說明這種遞歸的 SQL 查詢嗎?
這是一個獨立的示例。
Declare @Temp table
(
ID int,
ParentID int,
Happened date,
Value int
)
Insert into @Temp Values
(1, null, dateadd(day,1,GetDate()),1),
(2, 1, dateadd(day,2,GetDate()),2),
(3, 1, dateadd(day,3,GetDate()),3),
(4, null, dateadd(day,4,GetDate()),10),
(5, 3, dateadd(day,5,GetDate()),50),
(6, 4, dateadd(day,5,GetDate()),50),
(7, 5, dateadd(day,5,GetDate()),90);
----------------------------------------
with Magic as
(
select *
from @Temp
Where ID = 1
union all
select t.*
from
Magic m
inner join
@Temp t
on t.ParentID = m.ID
)
select * from Magic
option (maxrecursion 3)
CREATE TABLE ATable (ID INTEGER, ParentID INTEGER)
INSERT INTO ATable
SELECT 1, NULL
UNION ALL SELECT 2, 1
UNION ALL SELECT 3, 2
;WITH q AS (
SELECT ID, ParentID
FROM ATable
UNION ALL
SELECT a.ID, a.ParentID
FROM ATable a
INNER JOIN q ON q.ID = a.ParentID
)
SELECT DISTINCT *
FROM q
請查看以下鏈接,了解如何使用公用表表達式編寫遞歸查詢: http : //msdn.microsoft.com/en-us/library/ms186243.aspx
看看並閱讀:
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