Question

I have a table with 200 columns (maybe more…)

a1   a2   a3     a4  a5  ...a200
---------------------------------
1.2  2.3  4.4   5.1  6.7... 11.9   
7.2  2.3  4.3   5.1  4.7... 3.9   
1.9  5.3  3.3   5.1  3.7... 8.9   
5.2  2.7  7.4   9.1  1.7... 2.9  

I would like to compute many operations:

• SUM(every column)
• AVG(every column)
• SQRT(SUM(every column))
• POWER(SUM(every column),2)
• MIN(all columns)
• MAX(all columns)

• GREATEST(SUM(one column) vs SUM(other column))
  something like finding wich sum is greatest for every column:

  a1 vs a2,  a1 vs a3, a1 vs a4....,a1 vs a200,
  a2 vs a1,  a2 vs a3, a4 vs a5....,a2 vs a200,  
  ...
  a200 vs a1, a200vs a2, a200vs a3.....a200 vs a199
  

If I do a single select statement for each column,and for each operation I’d have:

SELECT 
 SUM(a1),...,SUM(a200),
 AVG(Sum(a1)),...,AVG(Sum(a200)),
 POWER(Sum(a1),2),...,POWER(Sum(a200),2),
 GREATEST(SUM(a1),SUM(a2)), GREATEST(SUM(a1),SUM(a3)),...,GREATEST(SUM(a1),SUM(a200)),
 GREATEST(SUM(a2),SUM(a1)), GREATEST(SUM(a2),SUM(a3)),...,GREATEST(SUM(a2),SUM(a200))....
 GREATEST(SUM(a200),SUM(a1)), GREATEST(SUM(a200),SUM(a3)),...,GREATEST(SUM(a200),SUM(a199))
 etc... FROM tabMultipleColumns

The problem here is when I do a query with more than 1024 possible results
aka, >= 1024 columns

Is there a way to keep doing massive operations with data doing a single scan of the table, I mean avoiding doing multiple selects statements?

I am trying to use only a scan, because if the table is huge (with size
of many GB’s) using many selects statements to scan the same table would be expensive…

Can a tool like BCP be used or what solution do you think is more efficient…

if you look only for the SUM, POWER(SUM(),2) and SQRT(SUM()), there are 600 result columns… if I keep doing this operations there are more than 1024…

Answer 1

That’s a lot of calculations. I would probably just do a periodic dump of them into another table to minimize server load. It depends on how often the query is going to be used though.