8/12/2019 Chronological Key

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Typically time dimension differs from all other dimensions in one way and thatis,

All other dimensions doesn't care about the order of the values in it.e.g. in region_dim the values are north, south, west and east. Here nobody wants to see whether north comes first or south comes first. i.e. no order is required here.

In the case of time dimension there needs to be a particular order for all the values present in it.e.g. 2010 is earliest and 2004 is older. Dec-10 is earliest and jan-10 is older. i.e. the values in the time dimension needs to follow a particular sorting order.So the chronological key is the key which tells the obiee that the data is incrementing based on the chronological column.

For defining a dimension to be a Time dimension, we need to have a chronological

Key.

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A. Typically time dimension differs from all other dimensions in one way and that is,

all other dimensions dont care about the order of the values in it.e.g. in region_dim the values are north, south, west and east. Here nobody wants to see whether north comes first or south comes first. i.e. no order is required here.

in the case of time dimension there needs to be a particular order for all the values present in it.e.g. 2010 is earliest and 2004 is older. Dec-10 is earliest and jan-10 is older. i.e. the values in the time dimensiion needs to follow a particular sorting order. So the chronological key is the key which tells the obiee that the data is incrementing based on the chronological column.

Here you may get another doubt. i.e. you are having columns like year, half_year, quarter, month, week and day. Here which one should become the chronolgocial key?

Analyse it yourself. If you kept year as chro key then obiee will be confused wh

ether jan-10 is earliest or feb-10 is earliest. Because it knows only that 2010is earliest and 2009 is older.

So always it should be the lowest level oif the dimension which needs to be thechronological key. In the abouve case it should be date.

You can select either date or date_id(this could be a sequence generator values).

2. what is the use time dimension?

8/12/2019 Chronological Key

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A.If all you want is to achieve drills from Month, Quarter and Year then treat it as a normal dimension and create the levels. But if you want to do calculations like YTD, QTD and MTD then you need to create a time dimension.

http://oraclebizint.wordpress.com/2007/11/05/oracle-bi-ee-101332-understanding-todate-and-ago-achieving-ytd-qtd-and-mtd/

Refer the above link for time dimension.