sql-cte | 易学教程

Printing tree with SQL CTE

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问题 The schema is as follows: CREATE TABLE [Structure]( [StructureId] [uniqueidentifier] NOT NULL, [SequenceNumber] [int] NOT NULL, -- order for siblings, unique per parent [ParentStructureId] [uniqueidentifier] NULL, CONSTRAINT [Structure_PK] PRIMARY KEY CLUSTERED ( [StructureId] ASC ) ) ON [PRIMARY] ALTER TABLE [Structure] WITH CHECK ADD CONSTRAINT [Structure_FK1] FOREIGN KEY([ParentStructureId]) REFERENCES [Structure] ([StructureId]) Currently, I can get all the logical data out with the

Maximum recursion has been exhausted

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问题 I need an efficient way to pass in a parameter [StartingNumber] and to count from [StartingNumber] sequentially until I find a number that is missing. I use the following sql to get the next number: DECLARE @StartOffset int SET @StartOffset = 23 ; With Missing as ( select @StartOffset as N where not exists( select * from [QUEUE] where QueueNum = @StartOffset AND ismelutash = 1) ), Sequence as ( select @StartOffset as N from [QUEUE] where QueueNum = @StartOffset union all select b.QueueNum

Deleting rows recursively in a self-referencing table using a CTE. How does the process take place?

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问题 I'm working on a side project, and in order to delete a row and all its descendants in a self-referencing table, I'm using a recursive CTE like this inside a trigger: CREATE TRIGGER dbo.tr_Comment_Delete ON dbo.Comment INSTEAD OF DELETE AS ;WITH IDs AS ( SELECT id FROM DELETED UNION ALL SELECT c.id FROM Comment AS c INNER JOIN IDs AS i ON c.parent_comment_id = i.id ) DELETE FROM Comment WHERE id IN (SELECT id FROM IDs); GO This is the self-referencing table Although I have this code working

Deleting rows recursively in a self-referencing table using a CTE. How does the process take place?

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I'm working on a side project, and in order to delete a row and all its descendants in a self-referencing table, I'm using a recursive CTE like this inside a trigger: CREATE TRIGGER dbo.tr_Comment_Delete ON dbo.Comment INSTEAD OF DELETE AS ;WITH IDs AS ( SELECT id FROM DELETED UNION ALL SELECT c.id FROM Comment AS c INNER JOIN IDs AS i ON c.parent_comment_id = i.id ) DELETE FROM Comment WHERE id IN (SELECT id FROM IDs); GO This is the self-referencing table Although I have this code working as expected, it is one of those cases in which you do something, but you're not quite sure how it works.

Printing tree with SQL CTE

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The schema is as follows: CREATE TABLE [Structure]( [StructureId] [uniqueidentifier] NOT NULL, [SequenceNumber] [int] NOT NULL, -- order for siblings, unique per parent [ParentStructureId] [uniqueidentifier] NULL, CONSTRAINT [Structure_PK] PRIMARY KEY CLUSTERED ( [StructureId] ASC ) ) ON [PRIMARY] ALTER TABLE [Structure] WITH CHECK ADD CONSTRAINT [Structure_FK1] FOREIGN KEY([ParentStructureId]) REFERENCES [Structure] ([StructureId]) Currently, I can get all the logical data out with the follow CTE, but I would like to print it directly in a depth first fashion. WITH SCTE (StructureId, Level,