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PODifficult T-SQL Join/Pivot
 

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  1. PODifficult T-SQL Join/Pivot
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    <p>The original way I worded this question would be unhelpful to most, so I've reworked it significantly.</p> <p>I have a legacy database, whose schema <strong>I have no control over</strong> (nor ever have). The db schema was designed agnostic of the provider for consumption by unmanaged C++, so there are no FK constraints, etc. I come along and need to consume this from .NET, and also need to present the data much differently than it was originally intended.</p> <p>Here is the schema of the relevant tables (I've bolded/asteriskifed what amount to the keys for this question):</p> <pre><code>CREATE TABLE [dbo].[Formats]( [GroupName] [varchar](255) NOT NULL, **[BatchID] [bigint] NOT NULL,** [SeriesNumber] [bigint] NOT NULL, **[SequenceID] [bigint] NOT NULL,** [SeqNum] [int] NOT NULL, [FormatName] [varchar](50) NOT NULL CREATE TABLE [dbo].[Fields]( [GroupName] [varchar](255) NOT NULL, **[BatchID] [bigint] NOT NULL,** **[SequenceID] [bigint] NOT NULL,** [SeqNum] [int] NOT NULL, **[FieldName] [varchar](50) NOT NULL,** [FieldDisplayName] [varchar](50) NOT NULL, [FieldValue] [ntext] NULL </code></pre> <p>There is a 1:Many relationship between Formats:Fields.</p> <p>I need to query for a list of format rows. The challenges are several: + There is a compound foreign key. + I need to filter the formats to a subset that contains related Fields. + The related fields must match an arbitrary number of filter criteria before being inner-joined to the formats.</p> <p>So to walk through this: The Stored Proc receives the following table valued parameter:</p> <pre><code>_FieldDisplayName_ Field_Value Field 1 001 Field 2 002 </code></pre> <p>It then needs to filter the Fields table by those values.</p> <p>Since I needed to use ALL of the criteria and not just one of them, I did not know how work with this to retrieve something useful to join with, when I didn't know how many values I'd have, or what the FieldDisplayName values would be.</p> <p>@Joe Phillips was smart enough to see through the chaos and suggest that I needed to pivot the table. That's this:</p> <p><strong>Edit:</strong> The following is working to pivot the data, but I am not sure it is ideal. Still waiting on other ideas before supplying an answer.</p> <p>Instead of using a TVP, I'm using a temp table and dynamic SQL (and yes, I see the injection vulnerability):</p> <pre><code>IF OBJECT_ID('[tempdb].[dbo].[#FilterFields]') is not null Drop Table dbo.#FilterFields CREATE Table #FilterFields (FieldDisplayName varchar(50), FieldValue nvarchar(max)) /* Just some example data */ INSERT INTO #FilterFields (FieldDisplayName, FieldValue) VALUES ('PTNUM', '011') INSERT INTO #FilterFields (FieldDisplayName, FieldValue) VALUES('SITENUM', '001') Declare @column_names varchar(max) Declare @dynamic_pivot_query as varchar(max) SELECT @column_names = Stuff((SELECT DISTINCT ',[' + FieldDisplayName + ']' FROM #FilterFields FOR xml path('')),1,1,'') PRINT(@column_names) SET @dynamic_pivot_query = 'select * ' + 'from tempdb.dbo.#FilterFields ' + 'Pivot ( MIN( FieldValue ) FOR FieldDisplayName IN (' + @column_names + ') ) as P' PRINT(@dynamic_pivot_query) EXEC(@dynamic_pivot_query) </code></pre>
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    1. COI think you're looking to pivot the data?
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    2. COActually, that's an interesting idea -- I hadn't thought of that. Let me dig into that. I don't think I even realized previously that T-SQL had a pivot function.
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    3. COCould you post some example data and the expected output? It is not quite clear (at least to me) what you are looking for.
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      1. USSebastian Meine
 

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