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POSQL join to multipe columns
 

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  1. POSQL join to multipe columns
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    <p>I have tables like this:</p> <pre><code>tbl_base id primary_id aaaa bbbb cccc dddd eeee tbl_current id current_id aaaa bbbb qqqq cccc dddd zzzz tbl_results id value aaaa 10 cccc 20 dddd 50 zzzz 10 eeee 5 </code></pre> <p>I have a table of results (<code>tbl_results</code>) that match to a given ID. I want to join this data to <code>tbl_base</code>. Unfortunately, there are four possible ID's that could appear in tbl_results:</p> <ol> <li>tbl_base.id </li> <li>tbl_base.primary_id </li> <li>tbl_current.current_id (tbl_current.id = tbl_base.id)</li> <li>tbl_current.current_id (tbl_current.id = tbl_base.primary_id)</li> </ol> <p>I want to build a left join for <code>tbl_results</code> to <code>tbl_base</code>:</p> <pre><code>SELECT * FROM tbl_base LEFT JOIN tbl_results ON tbl_results.id = tbl_base_id ... </code></pre> <p>What is the most efficient way to construct the query so that I join <code>tbl_results.id</code> to the four possible permutations of ID's present? I tried:</p> <pre><code>SELECT * FROM tbl_base LEFT JOIN tbl_current ON tbl_current.id = tbl_base.id LEFT JOIN tbl_results ON (tbl_results.id = tbl_base.id OR tbl_results.id = tbl_base.primary_id OR tbl_results.id = tbl_current.id OR tbl_results.id = tbl_current.current_id) </code></pre> <p>This doesn't work. The problem is that these tables are large in real life with millions of records and possible connections between all the ID's. I cannot change the structure of the tables in any way - I'm just working with the system I'm given. Any thoughts on how to do this with maximum efficiency? I just want to return any rows in <code>tbl_results</code> where it's ID matches any of the four possible ID's.</p> <p><strong>UPDATE:</strong></p> <p>This is the output I'm after:</p> <pre><code>id value aaaa 10 bbbb NULL cccc 20 dddd 50 --from 'dddd' dddd 10 --from 'zzzz' </code></pre>
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    1. USJeffrey Kramer
    1. USJeffrey Kramer
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    1. COI vote for union query.
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      1. POSQL join to multipe columns
      1. USDan Bracuk
    2. COhow does the query not work?
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      1. POSQL join to multipe columns
      1. USAndrew
    3. COPlease show the desired Output. It is not completely clear how the tables interact. In your example data there are no matches between tbl_base and table_current, as table_current.current_id does nowhere exist in table_base. Is that true?
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      1. POSQL join to multipe columns
      1. USThorsten Kettner
 

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