1, information is almost always used for two purposes: the preservation of operational records and the development of analytical decision-making. Simply put, the operational system saves the data, while the DW/BI system uses the data.
2,
From the definition of the chain is very simple, wujie the answer is very clear, I would add to the scope of the application of the two:
This year is a period of the same period compared with last year, applied to observe the change of an indicator in different years, the advantage is to remove most of the business of the seasonal factors, such as recruitment, February is off season, March is the peak season, do the March analysis with the actual show is the recruitment market changes, Instead of a change in company sales, the year-to-date growth can be seen, and the disadvantage is that flexibility is low, because most of the year (otherwise less than the goal of removing seasonal factors), does not reflect the short-term changes in the data.
The chain is a phase with a period equal to the period of comparison, such as last week and this week, last month and this month, the last quarter and this quarter, and so on, to indicate the continuous trend of data, the advantage is for high-speed growth business, can very well reflect the business growth trends and events impact (typical such as the new site traffic, UV first week 100, the second week 300, the third week 500, the fourth week to do an activity, 2000, Fifth week 1000, then the first three weeks of the site's user growth trend is very good, fourth week data has a sudden increase, can see the growth of the activity is very obvious), disadvantage is the light to see the number of difficult to exclude seasonal factors And for stable volatility data (such as the number of departments, each month into a, the trend in a year is not clear, but the size of the department has been expanding year-on-day), the trend is not obvious, the chain meaning is relatively small.
Data analysis Notes
