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POSql query to return elements with same ID as comma separated string
 

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  1. POSql query to return elements with same ID as comma separated string
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    <p>I have two tables, <code>table1</code> has a <code>entry_ID</code>, <code>entry_date</code> and other entry information. <code>table2</code> has <code>entry_ID</code> and <code>entry_subject</code>. Each <code>entry_ID</code> can have arbitrarily many <code>entry_subjects</code>.</p> <p>I want a query that will return an <code>entry_ID</code>, <code>entry_date</code>, and a list of the subjects corresponding to that entry separated by commas. </p> <p>The first step in this seems to be just getting a query that returns an <code>entry_ID</code> and a comma separated list of subjects from <code>table2</code>. Once I have that the join should be easy.<br> I adapted the <a href="http://www.projectdmx.com/tsql/rowconcatenate.aspx" rel="nofollow">recursive CTE method from this site</a>: to fit my case:</p> <pre><code>WITH RECURSIVE CTE (entry_ID, subjectlist, subject, length) AS ( SELECT entry_ID, cast( '' as varchar(8000)) , cast( '' as varchar(8000)), 0 FROM table2 GROUP BY entry_ID UNION ALL SELECT t2.entry_ID, cast(subjectlist || CASE length = 0 THEN '' ELSE ', ' END || entry_subject AS varchar(8000) ), cast (t2.entry_subject as varchar(8000)), length +1 FROM CTE c INNER JOIN table2 t2 on c.entry_ID=t2.entry_ID where t2.entry_subject &gt; c.subject) SELECT entry_ID, subjectlist FROM ( SELECT entry_ID, subjectlist, RANK() OVER ( PARTITION BY entry_ID order by length DESC) FROM CTE) D (entry_ID, subjectlist, rank) where rank = 1; </code></pre> <p>And it works, I get the response I expect. To achieve my final goal the query I use is this:</p> <pre><code>SELECT t1.* t2.subjectlist FROM table1 JOIN (ABOVE QUERY) AS t2 on t1.entry_ID=t2.entry_ID; </code></pre> <p>This seems very unwieldy. Is this really the best way to do this?</p>
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    1. USErwin Brandstetter
    1. USSnitse
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    1. COPersonally, I'd do this in a middle layer, off the database, if possible.
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      1. USAustin Salonen
    2. COWhat do you mean by middle layer? I suppose I could do this much more easily in a bash script that makes database calls, but I'm using a utility library that takes input strings that it interprets as querys and executes directly in the appropriate database.
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      1. POSql query to return elements with same ID as comma separated string
      1. USSnitse
    3. COOh, I didn't get that distinction. Yes thats what I mean.
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      1. USSnitse
 

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