I need to grab an additional row based on a variable result

Posted on 2013-12-19
Medium Priority
Last Modified: 2013-12-22

when l1.completed > startDate AND a.name LIKE '%Disable%'  

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true of the first row in the result set, I need to grab the previous row in the database and include it in the result set

CREATE PROCEDURE reportFreeCoolingTrackerDateTest (
        IN fromDate varchar (50),
        IN toDate varchar (50),
        IN timeZone varchar (50))

            DECLARE startDate varchar (50);
            DECLARE endDate varchar (50);
            DECLARE mylogID Int;
             SET startDate = FROM_UNIXTIME(fromDate/1000);
             SET endDate = FROM_UNIXTIME(toDate/1000);
        when l1.completed > startDate AND a.name LIKE '%Disable%' 
            THEN (time_to_sec(timediff(l1.completed,(CONVERT_TZ( (FROM_UNIXTIME(fromDate/1000)),'UTC', timeZone) ))) / 3600)
       END AS newTime,l1.recordId,
    DATABASE() AS databaseName, ((l1.item31985 - l1.item31987)*(time_to_sec(timediff(t2.completed, l1.completed)))) / 3600  AS kwDifference,
    ((l1.item31985 - l1.item31987) *  (substr(l.details, instr(l.details , ':' ) +1))) AS cost,
    (((l1.item31985 - l1.item31987) *  (substr(l.details, instr(l.details , ':' ) +1)))
    *(time_to_sec(timediff(t2.completed, l1.completed)) / 3600))  AS costT,
      time_to_sec(timediff(t2.completed, l1.completed)) / 3600 AS coolingHours,
      time_to_sec(timediff(endDate, startDate)) / 3600 AS totalTimeRange,l1.completed, 
     (CONVERT_TZ( (FROM_UNIXTIME(fromDate/1000)),'UTC', timeZone) )AS StartingDate, 
     (CONVERT_TZ( (FROM_UNIXTIME(toDate/1000)),'UTC', timeZone) ) AS EndingDate,   
      timeZone  AS timeZonePassed

  FROM logs l 
      INNER JOIN groups g ON g.groupId = l.groupId
      LEFT JOIN groups g1 ON g.parentId = g1.groupId
      LEFT JOIN groups g2 ON g1.parentId = g2.groupId
      LEFT JOIN groups g3 ON g2.parentId = g3.groupId                
      INNER JOIN activities a ON l.logId = a.logId 
      INNER JOIN log1644 l1 ON a.activityId = l1.activityId 
      INNER JOIN log1644 t2 ON t2.recordId = l1.recordid + 1
      INNER JOIN items i ON l.logId = i.logId AND i.name LIKE '%KW%'
      INNER JOIN users u ON l1.userId = u.userId AND i.name LIKE '%KW%'
     WHERE i.itemID = "31985"  
      AND l1.started
        BETWEEN startDate
            AND endDate 
     ORDER BY l1.recordId,l1.started;
    END //


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Question by:portlight
  • 5
  • 3
LVL 15

Expert Comment

ID: 39731250
You should create a cursor to access to the rows of the select. By creating a cursor you can process rows one by one: save the current row to a variable, maintaining the previous row on another variable (so you will need two row variables).

Please see this article about cursors on MySQL: http://dev.mysql.com/doc/refman/5.0/en/cursors.html

Author Comment

ID: 39731266
I have not used cursors before, is it difficult to convert what I have to function as you are talking of.
LVL 15

Expert Comment

ID: 39731281
Have you read the article? I think it shouldn't be difficult.

I would do it for you but the problem is I don't really understand what exactly you want. You said: "if (this) true of the first row in the result set, I need to grab the previous row in the database and include it in the result set ". Never exist a previous row of first row.
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LVL 15

Expert Comment

ID: 39731288
Also you can get first row just by adding a "TOP 1" just after SELECT word. This will make the SELECT to return just the first record instead of all records.

Then, you can also use variables to assign the value of columns when the SELECT statement returns exactly one row:

SELECT @myvar1=mycolumn1, @myvar2=mycolumn2, ...., @myvarN = mycolumnN
FROM bla bla....

Author Comment

ID: 39732096
If the initial query grabs 10 of 100 rows - the first row of the result set being row 24 AND that first row meets this condition
when l1.completed > startDate AND a.name LIKE '%Disable%'  

Then I need to figure out how to include row 23 in the result set. Even if the started time is outside of the between dates
LVL 15

Expert Comment

ID: 39732566
Then I think you should do this:

store the recordId of the found record on a variable (for example v_id).

then make this query:

SELECT @v_previous_id = MAX(recordId)
FROM logl644
WHERE recordId < @v_id;

Then you can get the previous record by issuing this sentence:

FROM your_tables_and_join
WHERE ll.recordId = @v_previous_id;

Author Comment

ID: 39732594
The problem that i have been running into is this creates two return data sets when the query has been run - is there any way to incorporate this into one return set.
LVL 15

Accepted Solution

gplana earned 2000 total points
ID: 39732662
You can create a dynamic sql, i.e. create programmatically the SQL string (by adding the additional SELECTS with the clause UNION) and execute this string.

Please look at this article for more information about dynamic SQL.


Also please look this article for how to use UNION:


Hope it helps. Regards.

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