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Re: Please help me write a query

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Got it:
    SELECT state1, timestamp 
       FROM (SELECT state1, timestamp, lag(state1) OVER (ORDER BY timestamp) FROM test) as foo 
     WHERE state1 != lag OR lag IS NULL 
ORDER BY timestamp;
 state1 |         timestamp          
--------+----------------------------
      1 | now() - interval '12 hours'
      2 | now() - interval '9 hours'
      1 | now() - interval '8 hours'

Without lag IS NULL I miss the first row.

On Thu, May 27, 2010 at 11:44 AM, Nikolas Everett <nik9000@xxxxxxxxx> wrote:
The 10 and 11 hour interval are being skipped because I'm only interested in the transitions of state 1. State 1 only transitioned three times at now - 12, now - 9 and now - 8.

The table has both transitions in it because I frequently care about them both together.  I just don't in this case.


On Thu, May 27, 2010 at 12:36 PM, Justin Graf <justin@xxxxxxxxxxxx> wrote:
On 5/27/2010 9:45 AM, Nikolas Everett wrote:
Sorry.  Here is the setup:
CREATE TABLE test (id BIGSERIAL PRIMARY KEY, state1 INT NOT NULL, state2 INT NOT NULL, timestamp TIMESTAMP);
INSERT INTO test (state1, state2, timestamp) VALUES (1, 1, now() - interval '12 hours');
INSERT INTO test (state1, state2, timestamp) VALUES (1, 2, now() - interval '11 hours');
INSERT INTO test (state1, state2, timestamp) VALUES (1, 1, now() - interval '10 hours');
INSERT INTO test (state1, state2, timestamp) VALUES (2, 1, now() - interval '9 hours');
INSERT INTO test (state1, state2, timestamp) VALUES (1, 1, now() - interval '8 hours');


I want to write a query that spits out:
 state1 |         timestamp          
--------+----------------------------
      1 | now() - interval '12 hours'
      2 | now() - interval '9 hours'
      1 | now() - interval '8 hours'


Have a question what makes  these values different other than the timestamp???


1, 1, now() - interval '12 hours'
1, 1, now() - interval '10 hours'

The reason i ask, is because you show 1, 1, now() - interval '8 hours'  in the desired output.   What logic keeps the 8 hour and 12 hour but not the 10hour interval???

Its kinda hard to understand why the 10hour interval is being skipped???


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