Usage of aggregate functions- Rank and Ceiling while using enrichment and query activity in adobe campaign classic

Hi All,

Can you please help to tell me 

Usage of aggregate functions- Rank and Ceiling while using enrichment and query activity in adobe campaign classic

example when we use enrichment activity and create custom column for calculations, May I please know when to use below Aggregate functions and their usage??

Usage of aggregate functions- Rank and Ceiling while using enrichment and query activity in adobe campaign

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