Recursive SQL

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Recursive SQL

syedathariqbal

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Points: 3175
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May 10, 2013 at 3:46 am

#272459

Hi All,
Need help on some recursive Data. I would need to get 4 records out of below available If I pass value 395. Since, for 395, COlD (Child of ColA) has value 394. Again we check ColaA for 394 and find the corresponding value in ColD which is 347. Again in ColA 347 corresponds to 0 value in ColD. Total of 4 records.
ColA ColB ColC ColD ColE ColF
347 AA 25 0 0 0
362 BB 25 347 0 50
363 CC 25 362 0 51
364 DD 25 347 0 50
365 EE 25 364 0 51
367 FF 25 365 0 54
369 GG 25 347 0 50
373 HH 25 347 0 50
374 II 25 373 0 51
375 JJ 25 374 0 54
376 KK 25 374 0 54
394 LL 25 347 0 50
395 MM 25 394 0 51
I beleive Using While loop this can be done. Any suggestions ?

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ChrisM@Work SSC Guru Points: 186127 More actions · Answer 1

syedathariqbal (5/10/2013)
Hi All,
Need help on some recursive Data. I would need to get 4 records out of below available If I pass value 395. Since, for 395, COlD (Child of ColA) has value 394. Again we check ColaA for 394 and find the corresponding value in ColD which is 347. Again in ColA 347 corresponds to 0 value in ColD. Total of 4 records.
ColA ColB ColC ColD ColE ColF
347 AA 25 0 0 0
362 BB 25 347 0 50
363 CC 25 362 0 51
364 DD 25 347 0 50
365 EE 25 364 0 51
367 FF 25 365 0 54
369 GG 25 347 0 50
373 HH 25 347 0 50
374 II 25 373 0 51
375 JJ 25 374 0 54
376 KK 25 374 0 54
394 LL 25 347 0 50
395 MM 25 394 0 51
I beleive Using While loop this can be done. Any suggestions ?

Sure: set this table up as a CREATE TABLE & INSERTs to populate it, test that the script executes without errors, then post it here.

^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden

syedathariqbal Hall of Fame Points: 3175 More actions · Answer 2

Here it is....

CREATE TABLE [dbo].[tmpTable](

[ColA] [nchar](10) NOT NULL,

[ColB] [nchar](10) NULL,

[ColC] [nchar](10) NULL,

[ColD] [nchar](10) NULL,

[ColE] [nchar](10) NULL,

[ColF] [nchar](10) NULL,

CONSTRAINT [PK_tmpTable] PRIMARY KEY CLUSTERED

(

[ColA] ASC

)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]

) ON [PRIMARY]

GO

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'347 ', N'A ', N'25 ', N'0 ', N'0 ', N'0 ')

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'362 ', N'B ', N'25 ', N'347 ', N'0 ', N'50 ')

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'363 ', N'C ', N'25 ', N'362 ', N'0 ', N'51 ')

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'364 ', N'D ', N'25 ', N'347 ', N'0 ', N'50 ')

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'365 ', N'E ', N'25 ', N'364 ', N'0 ', N'51 ')

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'367 ', N'F ', N'25 ', N'365 ', N'0 ', N'54 ')

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'369 ', N'G ', N'25 ', N'347 ', N'0 ', N'50 ')

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'373 ', N'H ', N'25 ', N'347 ', N'0 ', N'50 ')

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'374 ', N'I ', N'25 ', N'373 ', N'0 ', N'51 ')

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'375 ', N'J ', N'25 ', N'374 ', N'0 ', N'54 ')

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'376 ', N'K ', N'25 ', N'374 ', N'0 ', N'50 ')

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'394 ', N'L ', N'25 ', N'347 ', N'0 ', N'50 ')

INSERT [dbo].[tmpTable] ([ColA], [ColB], [ColC], [ColD], [ColE], [ColF]) VALUES (N'395 ', N'M ', N'25 ', N'394 ', N'0 ', N'51 ')

Mark Cowne One Orange Chip Points: 26952 More actions · Answer 3

I get 3 rows not 4, maybe I'm missing something.

DECLARE @Start INT = 395;

WITH Recur AS (

SELECT [ColA], [ColB], [ColC], [ColD], [ColE], [ColF]

FROM [dbo].[tmpTable]

WHERE [ColA] = @Start

UNION ALL

SELECT t.[ColA], t.[ColB], t.[ColC], t.[ColD], t.[ColE], t.[ColF]

FROM [dbo].[tmpTable] t

INNER JOIN Recur r ON r.[ColD] = t.[ColA])

SELECT [ColA], [ColB], [ColC], [ColD], [ColE], [ColF]

FROM Recur;

____________________________________________________

Deja View - The strange feeling that somewhere, sometime you've optimised this query before

How to get the best help on a forum

http://www.sqlservercentral.com/articles/Best+Practices/61537

ChrisM@Work SSC Guru Points: 186127 More actions · Answer 4

Thanks...

WITH Resolver AS (

SELECT

[Level] = 1,

[Route] = CAST(RTRIM(t.ColA) AS VARCHAR(25)),

t.ColA, t.ColB, t.ColC, t.ColD, t.ColE, t.ColF

FROM tmpTable t

WHERE ColA = 395

UNION ALL

SELECT

[Level] = r.[Level] + 1,

[Route] = CAST(r.[Route] + '>' + CAST(RTRIM(t.ColA) AS VARCHAR(25)) AS VARCHAR(25)),

t.ColA, t.ColB, t.ColC, t.ColD, t.ColE, t.ColF

FROM Resolver r

INNER JOIN tmpTable t ON t.ColA = r.ColD

)

SELECT *

FROM Resolver

ORDER BY [Level], ColA;

-- three rows are returned: There is no row with value=0 in ColA.

^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden

ChrisM@Work SSC Guru Points: 186127 More actions · Answer 5

Quick work, Mark 😉

^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden

syedathariqbal Hall of Fame Points: 3175 More actions · Answer 6

syedathariqbal

Hall of Fame

Points: 3175

May 10, 2013 at 5:46 am

#1614146

Thanks Chris and Mark. Exactly what I needed.

Jeff Moden SSC Guru Points: 1004356 More actions · Answer 7

syedathariqbal (5/10/2013)
Thanks Chris and Mark. Exactly what I needed.

The next question would be.... do you know how it works?

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)