How calculate the percentage of area

[jmodic]

You need FULL OUTER JOIN for that. Check the 9i SQL manual for the syntax.

Or another option would be to union-all all four tables and then do your math from there. So the inline view you would use as a starting point would be something like:

select 'TI' AS tbl, LS_ID, SUM(AREA) AS area from area_ti
group by LS_ID
union all
select 'TO' AS tbl, LS_ID, SUM(AREA) AS area from area_to
group by LS_ID
union all
select 'FI' AS tbl, LS_ID, SUM(AREA) AS area from area_fi
group by LS_ID
union all
select 'EM' AS tbl, LS_ID, SUM(AREA) AS area from area_em
group by LS_ID