SQL & PL/SQL :: Oracle 9i - Conditional Statement

The conditional statements should not only be executed in sequence, but also if any of them are true they should not be overridden by any subsequent conditional statements being true.

When actual effort Accepted or Rejected for AST proposals and calculate a flag for "enhance to AST guideline" = Y/N as follows for each employee and display at the employee level

1)If AST eligibility = N AND proposed AST % >0, then "N"
2)Else If AST eligibility = N AND proposed AST % = 0 then "n/a"
3)Else If AST eligibility = Y AND Act Rank = 3 AND proposed AST = 0 then "Y"
4)Else If AST eligibility = Y AND Act Rank = 3 AND proposed AST >0 then "N"
5)Else If AST eligibility = Y AND Act Rank = 2 AND proposed AST = 0 then "Y"
6)Else If AST eligibility = Y AND AST % is greater than or equal to the AST guideline minimum AND less than or equal to the AST guideline maximum, then "Y"
7)Else If AST eligibility = Y AND AST % is less than the minimum guideline OR greater than the maximum guideline, then "N"

I tried the following code but I am not getting the expected result .

if (upper(P_stat)='ACCEPTED' or upper(P_stat) like 'REJECTED%') then
else if NVL(P_elgi,'N') <> 'Y' AND P_prop > '0' then
P_flag := 'N';
else if(NVL(P_elgi,'N') <> 'Y' AND P_prop = '0') then
[code]........