Question

I’ll simplify the problem as much as possible:

I have an oracle table:

row_priority, col1, col2, col3 0, .1, 100, {null} 12, {null}, {null}, 3 24, .2, {null}, {null} 

Desired result:

col1, col2, col3 .2, 100, 3 

So according to the priority of the row, it overrides previous row values, if given.

I’m attempting to work out a solution using analytical functions over the table, but it just isn’t behaving…

I try:

select last_value(col1 ignore nulls) over () col1,        last_value(col2 ignore nulls) over () col2,        last_value(col3 ignore nulls) over () col3 from (select * from THE_TABLE order by row_priority) where rownum = 1 

or the inverse:

select first_value(col1 ignore nulls) over () col1,        first_value(col2 ignore nulls) over () col2,        first_value(col3 ignore nulls) over () col3 from (select * from THE_TABLE order by row_priority desc) where rownum = 1 

And neither seem to ignore nulls. Any hints?

Answer 1

You need to put rownum = 1 OUTSIDE the analytical query

SELECT  * FROM    (   select          last_value(col1 ignore nulls) over () col1,                             last_value(col2 ignore nulls) over () col2,                             last_value(col3 ignore nulls) over () col3             from (select * from THE_TABLE ORDER BY ROW_PRIORITY)         ) WHERE   ROWNUM = 1 

which results in (using your values above):

COL1   COL2    COL3 ------ ------- ---- 0.2    100     3