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POHow do I convert a many-to-many relationship from 2-column table?
 

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  1. POHow do I convert a many-to-many relationship from 2-column table?
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    <p>Suppose I have this database table (some sample code below) that stores the relationship between two lists (requirements and testcases in my case) and I want to create a table with rows showing testcases and columns showing requirements with an indicator showing that a relationship exists.</p> <p>A few limitations</p> <ul> <li>I don't have the luxury of changing the db structure as this belongs to an open source test case management system (TestLink).</li> <li>It's possible to write some code for this, but I'm hoping it can be done in MySQL.</li> <li>Ah, and yes, it uses MySQL, so this would have to work in that environment.</li> <li><p>This functionality used to exist, but has been taken out because typically, this type of work brings the db to its knees when there are tens-of-thousands of testcases and requirements.</p> <p>create table <code>pivot</code> ( <code>req_id</code> int(11), <code>testcase_id</code> int(11) ) ;</p> <p>/*Data for the table <code>pivot</code> */ </p> <p>insert into <code>pivot</code>(<code>req_id</code>,<code>testcase_id</code>) values (1,1); </p> <p>insert into <code>pivot</code>(<code>req_id</code>,<code>testcase_id</code>) values (2,2); </p> <p>insert into <code>pivot</code>(<code>req_id</code>,<code>testcase_id</code>) values (3,3); </p> <p>insert into <code>pivot</code>(<code>req_id</code>,<code>testcase_id</code>) values (4,1); </p> <p>insert into <code>pivot</code>(<code>req_id</code>,<code>testcase_id</code>) values (5,2); </p> <p>insert into <code>pivot</code>(<code>req_id</code>,<code>testcase_id</code>) values (6,3); </p> <p>insert into <code>pivot</code>(<code>req_id</code>,<code>testcase_id</code>) values (2,1); </p> <p>insert into <code>pivot</code>(<code>req_id</code>,<code>testcase_id</code>) values (3,2); </p></li> </ul> <p>What I want to get out of the query is a table that looks somethign like this:</p> <pre><code> 1 2 3 4 5 6 1 x x x 2 x x x 3 x x </code></pre> <p>Note:the row are the testcase_ids and the columns are the 'req_ids'</p> <p>Anyone have a tip on how to get this with just SQL?</p>
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    1. USnot-bob
    1. USnot-bob
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    1. COYou're trying to generate a report of a relational model, this isn't something you should be doing in SQL. SQL is an engine for reliably storing and returning structured data, not for formatting data. A reporting tool or even a spreadsheet will easily be able to pivot this data for you.
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      1. POHow do I convert a many-to-many relationship from 2-column table?
      1. USMyItchyChin
    2. COIf you have a known set of testcase_ids then you can write a tedious series of left joins to get the result. If you don't know, then you could generate the series of left joins as a dynamic query, then put that together into the afore mentioned tedious query. It's tedious and unpleasant either way.
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      1. POHow do I convert a many-to-many relationship from 2-column table?
      1. USGriffin
    3. COThe testcases would grow over time (as would the list of requirements) so a generalized way to accomplish this would be the preferred way.
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      1. POHow do I convert a many-to-many relationship from 2-column table?
      1. USnot-bob
 

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Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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