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From Les Hartzman <>
Subject Re: Wide rows/composite keys clarification needed
Date Mon, 21 Oct 2013 23:27:37 GMT
So looking at Patrick McFadin's data modeling videos I now know about using
compound keys as a way of partitioning data on a by-day basis.

My other questions probably go more to the storage engine itself. How do
you refer to the columns in the wide row? What kind of names are assigned
to the columns?

On Oct 20, 2013 9:34 PM, "Les Hartzman" <> wrote:

> Please correct me if I'm not describing this correctly. But if I am
> collecting sensor data and have a table defined as follows:
>          create table sensor_data (
>                sensor_id int,
>                time_stamp int,  // time to the hour granularity
>                voltage float,
>                amp float,
>                PRIMARY KEY (sensor_id, time_stamp) ));
> The partitioning value is the sensor_id and the rest of the PK components
> become part of the column name for the additional fields, in this case
> voltage and amp.
> What goes into determining what additional data is inserted into this row?
> The first time an insert takes place there will be one entry for all of the
> fields. Is there anything besides the sensor_id that is used to determine
> that the subsequent insertions for that sensor will go into the same row as
> opposed to starting a new row?
> Base on something I read (but can't currently find again), I thought that
> as long as all of the elements of the PK remain the same (same sensor_id
> and still within the same hour as the first reading), that the next
> insertion would be tacked onto the end of the first row. Is this correct?
> For subsequent entries into the same row for additional voltage/amp
> readings, what are the names of the columns for these readings? My
> understanding is that the column name becomes a concatenation of the
> non-row key field names plus the data field names.So if the first go-around
> you have <time_stamp>:<voltage> and <time_stamp>:<amp>, what
do the
> subsequent column names become?
> Thanks.
> Les

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