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Query syntax - PIVOT?

Posted on 2013-11-19
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Last Modified: 2013-11-19
Hello,

I have a tabled defined as:

CREATE TABLE [dbo].[DocumentData](
	[doc_id] [int] NOT NULL,
	[ddt_FieldName] [nvarchar](20) NULL,
	[ddt_FieldValue] [nvarchar](100) NULL,
	[ddt_Changed] [bit] NULL,
	[ddt_ChangedUserId] [int] NULL,
	[ddt_ChangedDateTime] [datetime] NULL,
	[id] [int] IDENTITY(1,1) NOT NULL
) ON [PRIMARY]

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It contains data collected from a document - identified by doc_id.  

For each document there are many rows where each row is a field name and a field value.

If i know that my document has ddt_FieldNames of A, B, C and D how would i write an sql statement to produce all the data in columns for document with doc_id 6?

I am looking for output like:

doc_id      A      B      C      D
6               10    66   12     13

where A, B, C, and D have respective ddt_FieldValues  of 10, 66, 12 , 13
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Question by:soozh
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Expert Comment

by:Louis01
ID: 39659016
Q1: I suppose the columns (A-D) comes from ddt_FieldNames?
Q2: Would it always be A, B, C & D? Can there be more names?
Q3: Do you need to sum ddt_FieldValues?
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Author Comment

by:soozh
ID: 39659032
Q1: I suppose the columns (A-D) comes from ddt_FieldNames?
Yes


Q2: Would it always be A, B, C & D? Can there be more names?
No

Q3: Do you need to sum ddt_FieldValues?
No


I just need a row of data for each document.

Thanks
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Expert Comment

by:Louis01
ID: 39659034
Your response of No to Q2:
No, there can be more names or No, it would always be ABC&D?

Q4: What to do when no row is found for ddt_FieldNames?
Q5: What to do when there us more than one of the same value in ddt_FieldNames?
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Author Comment

by:soozh
ID: 39659041
It should Always be A B C and D

Q4: return null as the value

Q5:  There should only be one row in the table for each document so i expect that i would have to add the document number to the final Query.
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Expert Comment

by:Louis01
ID: 39659050
The simplest way to achieve this would be:
select [doc_id]
     , CASE [ddt_FieldName] WHEN 'A' THEN [ddt_FieldValue] ELSE 0 END as 'A'
     , CASE [ddt_FieldName] WHEN 'B' THEN [ddt_FieldValue] ELSE 0 END as 'B'
     , CASE [ddt_FieldName] WHEN 'C' THEN [ddt_FieldValue] ELSE 0 END as 'C'
     , CASE [ddt_FieldName] WHEN 'D' THEN [ddt_FieldValue] ELSE 0 END as 'D'
  from DocumentData

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Accepted Solution

by:
Louis01 earned 500 total points
ID: 39659057
You could use the PIVOT function as follows:
select [doc_id], [A], [B], [C], [D]
  from (select doc_id, ddt_FieldName, ddt_FieldValue
          from DocumentData) as pt_src
PIVOT (MAX(ddt_FieldValue) FOR ddt_FieldName IN ([A], [B], [C], [D])) as pt

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Expert Comment

by:PortletPaul
ID: 39659080
No points please.

Louis01, you forgot the max( ... ) and group by
select [doc_id]
     , MAX ( CASE [ddt_FieldName] WHEN 'A' THEN [ddt_FieldValue] ELSE 0 END ) as 'A'
     , MAX ( CASE [ddt_FieldName] WHEN 'B' THEN [ddt_FieldValue] ELSE 0 END ) as 'B'
     , MAX ( CASE [ddt_FieldName] WHEN 'C' THEN [ddt_FieldValue] ELSE 0 END ) as 'C'
     , MAX ( CASE [ddt_FieldName] WHEN 'D' THEN [ddt_FieldValue] ELSE 0 END ) as 'D'
  from DocumentData
group by [doc_id]

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I did exactly the same thing myself recently :)
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Author Closing Comment

by:soozh
ID: 39659082
The pivot worked.  The other solution created many rows.  Thanks.
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