Question

I have query like the following

SELECT a.*, b.*

(SELECT ATTR1, ATTR2, sum(QUANTITY) AS TOTAL_QTY,
ATTR3 FROM TABLE_A
WHERE ATTR4 > 0
GROUP BY ATTR1, ATTR2, ATTR3) a,

TABLE_B b

WHERE a.ATTR1 = b.ATTR1
AND a.ATTR2 = b.ATTR2

I need to GROUP BY only ATTR1 to calculate the correct TOTAL_QTY, but the only reason I am grouping other attributes because Oracle requires that if GROUP BY clause is present then all SELECT attributes should be in the GROUP BY clause too.

This means every time I need an attribute in this query from Table_A then I need to put it in GROUP BY too. That not only looks ugly, but can have performance impact and maybe unforseen side-effect.

How do I rewrite the above query to calculate the TOTAL_QTY in each ATTR1 groups, without the GROUP BY clause?

Answer 1

Use Oracle analytic functions. Change the inline view for table_a to something like:

select attr1,
       attr2,
       sum(quantity) over (partition by attr1 order by attr1) as total_qty,
       attr3
from   table_a
where  attr4 > 0

This may need tweaking a bit, but that’s the basic idea.