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    <p>Identifying non-consecutive values is always a bit tricky and involves several nested sub-queries (at least I cannot come up with a better solution).</p> <p>The first step is to identify non-consecutive values for the year:</p> <h3>Step 1) Identify non-consecutive values</h3> <pre><code>select company, profession, year, case when row_number() over (partition by company, profession order by year) = 1 or year - lag(year,1,year) over (partition by company, profession order by year) &gt; 1 then 1 else 0 end as group_cnt from qualification </code></pre> <p>This returns the following result:</p> <pre> company | profession | year | group_cnt ---------+------------+------+----------- Google | Programmer | 2000 | 1 Google | Sales | 2000 | 1 Google | Sales | 2001 | 0 Google | Sales | 2002 | 0 Google | Sales | 2004 | 1 Mozilla | Sales | 2002 | 1 </pre> <p>Now with the group_cnt value we can create "group IDs" for each group that has consecutive years:</p> <h3>Step 2) Define group IDs</h3> <pre><code>select company, profession, year, sum(group_cnt) over (order by company, profession, year) as group_nr from ( select company, profession, year, case when row_number() over (partition by company, profession order by year) = 1 or year - lag(year,1,year) over (partition by company, profession order by year) &gt; 1 then 1 else 0 end as group_cnt from qualification ) t1 </code></pre> <p>This returns the following result:</p> <pre> company | profession | year | group_nr ---------+------------+------+---------- Google | Programmer | 2000 | 1 Google | Sales | 2000 | 2 Google | Sales | 2001 | 2 Google | Sales | 2002 | 2 Google | Sales | 2004 | 3 Mozilla | Sales | 2002 | 4 (6 rows) </pre> <p>As you can see each "group" got its own group_nr and this we can finally use to aggregate over by adding yet another derived table:</p> <h3>Step 3) Final query</h3> <pre><code>select company, profession, array_agg(year) as years from ( select company, profession, year, sum(group_cnt) over (order by company, profession, year) as group_nr from ( select company, profession, year, case when row_number() over (partition by company, profession order by year) = 1 or year - lag(year,1,year) over (partition by company, profession order by year) &gt; 1 then 1 else 0 end as group_cnt from qualification ) t1 ) t2 group by company, profession, group_nr order by company, profession, group_nr </code></pre> <p>This returns the following result:</p> <pre> company | profession | years ---------+------------+------------------ Google | Programmer | {2000} Google | Sales | {2000,2001,2002} Google | Sales | {2004} Mozilla | Sales | {2002} (4 rows) </pre> <p>Which is exactly what you wanted, if I'm not mistaken.</p>
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    1. POGROUP BY and aggregate sequential numeric values
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    1. COThis absolutely 100% what I needed, and I very much appreciate all of the explanation and examples you've put into this!
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      1. USJoshua Burns
    2. COVery descriptive, and I also like the fact how this solution uses window functions of three different kinds (`sum()`, `row_number()`, `lag()`), making it a good material on how to use them (combined in one solution too).
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      1. USAndriy M
 

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