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Select Previous Row Values

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Join Date: Nov 2006

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dmmckelv

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Select Previous Row Values

Jul 18th, 2008

Is there a keyword in SQL that would allow you to select a value from a field in the previous row? I am looking for something that would give me the speed field value for the row before:

 Help with Code Tags 
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SELECT min(Parsed.Time), [Parsed.Number]
FROM Parsed
GROUP BY [Parsed.Rev Number]
SELECT min(Parsed.Time), [Parsed.Number]
FROM Parsed
GROUP BY [Parsed.Rev Number]

Last edited by dmmckelv; Jul 18th, 2008 at 4:58 am. Reason: more specific

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wujtehacjusz wujtehacjusz is offline

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Re: Select Previous Row Values

Jul 18th, 2008

You can always use join two tables using row_number()...

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dmmckelv

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Re: Select Previous Row Values

Jul 18th, 2008

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Originally Posted by wujtehacjusz

You can always use join two tables using row_number()...

My rows are not numbered. Any other suggestions?

Thanks!

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tesuji

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Re: Select Previous Row Values

Jul 20th, 2008

Hello dmmckelv,

When Edgar Frank Codd invited relational databases his primary idea was to found it on
logic algebra and set theory. The rows of relational tables (aka relations) are sets. Therefore, there aren't duplicate rows nor any particular order of rows. From this point of view, "I am looking for something that would give me the speed field value for the row before" is rather irrelevant.

However, to put any meaningful signification on it, your table must already have a column
which allows such an ordering, for example date, timestamp or auto-increment numbers.
If you don't have such special column (or set of columns) within a table, it is impossible to determine the predecessor of a specific row because the today predecessor could be the successor row tomorrow (e.g. due to inserting and deleting rows in the meantime).

To cut a long story short, what's that special column of your table to get particularly ordered rows? You may also post the creating statement of your table.

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tesu

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