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POSum of the most recent non-null columns (window function with "ignore nulls")
 

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  1. POSum of the most recent non-null columns (window function with "ignore nulls")
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    <p>I am using PostgreSQL 9.1.9.</p> <p>In the project I am working on, some most recent records have null columns because that information was not available when that row was created. I have a view that lists the sum of rows that belongs to the members of a group. As of right now, the view shows the sum of the most recent columns, which uses null values if those are the most recent values. For example, </p> <pre><code>table1 group_name | member ------------------- group1 | Andy group1 | Bob table2 name | stat_date | col1 | col2 | col 3 -------------------------------------- Andy | 6/19/13 | null | 1 | 2 Andy | 6/18/13 | 100 | 3 | 5 Bob | 6/19/13 | 50 | 9 | 12 Bob | 6/18/13 | 111 | 31 | 51 -- creating view would be something like this... create view v_grouped as select table1.group_name, stat_date, sum(col1) as col1_sum, sum(col2) as col2_sum, sum(col3) as col3_sum from table1 join table2 on table1.member = table2.name group by table1.group_name, table2.stat_date; </code></pre> <p>Current view looks like this:</p> <pre><code>group_name | stat_date | col1_sum | col2_sum | col3_sum ------------------------------------------------------- group1 | 6/19/13 | 50 | 10 | 14 group2 | 6/18/13 | 211 | 34 | 56 </code></pre> <p>Instead of 50, 150 would be a closer representation of what the actual group total is, despite lack of data for 6/19. So, I want an output of</p> <pre><code>group_name | stat_date | col1_sum | col2_sum | col3_sum ------------------------------------------------------- group1 | 6/19/13 | 150 | 10 | 14 group2 | 6/18/13 | 211 | 34 | 56 </code></pre> <p>I've been looking at <code>first_value()</code> from window functions as a possible function to use. I found that Oracle's <code>first_value()</code> supports the <code>ignore nulls</code> option which I believe will do what I want (<a href="http://psoug.org/definition/FIRST_VALUE.htm" rel="nofollow">http://psoug.org/definition/FIRST_VALUE.htm</a>). According to this page I linked, about PL/SQL's <code>first_value()</code> function: </p> <blockquote> <p>If the first value in the result set is NULL then the function returns NULL unless you specify IGNORE NULLS. If you use the IGNORE NULLS parameter then FIRST_VALUE will return the first non-null value found in the result set. (If all values are null then it will return NULL.)</p> <p>Example Syntax: FIRST_VALUE(expression [INGORE NULLS]) OVER (analytic_clause)</p> </blockquote> <p>But PostgreSQL's <code>first_value()</code> does not support such an option. Is there a way to do this in PostgreSql? Thank you in advance! </p>
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    1. USBeryllium
    1. USJi Mun
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    1. COshow us the sql
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    2. COI just included the sql script that goes along with the view. Thanks.
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      1. USJi Mun
    3. COI don't understand the explanation. You keep writing "most recent columns". Do you add columns in time? What do you mean by "most recent column"?
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