Any trick to sort columns?

Question

I have a particular issue to solve. I have a table as follows:
CREATE TABLE Trunk (
Port1 NUMBER,
Port2 NUMBER,
Port3 NUMBER
I will use a complex query to select 3 values from other places to populate Trunk table. On insertion, I'll have to make sure that Port1 < Port2 < Port3. Is there an easy trick to accomplish this?
So far I have this kind of stupid way to do it. As any savvy can see, if I have 4 columns to sort out, I will need a permutation of 24 subqueries in a big UNION. Doesn't scale well.
Please help. Thanks.
Matt
INSERT INTO Trunk VALUES (Port1, Port2, Port3)
SELECT x.Port, y.Port, z.Port FROM x, y, z
WHERE <expr> AND x.Port < y.Port AND y.Port < z.Port
UNION ALL
SELECT x.Port, z.Port, y.Port FROM x, y, z
WHERE <expr> AND x.Port < z.Port AND z.Port < y.Port
UNION ALL
SELECT y.Port, x.Port, z.Port FROM x, y, z
WHERE <expr> AND y.Port < x.Port AND x.Port < z.Port
UNION ALL
SELECT y.Port, z.Port, x.Port FROM x, y, z
WHERE <expr> AND y.Port < z.Port AND z.Port < x.Port
UNION ALL
SELECT z.Port, x.Port, y.Port FROM x, y, z
WHERE <expr> AND z.Port < x.Port AND x.Port < y.Port
UNION ALL
SELECT z.Port, y.Port, x.Port FROM x, y, z
WHERE <expr> AND z.Port < y.Port AND y.Port < x.Port;

Answer 1

Hi Friend
Inserting the values directly with insert,select statement is bit complex. i ve tried the combinations along with the functions decode and sign but it is too complex. the best alternative solution is like this . create a function as described below
create or replace function rec(a number, b number , c number) return varchar2 is
v varchar2(200);
begin
if (a>=b) and (b >=c) then           /* a>b>c */
v:= a||'|'||b||'|'||c;
elsif (a >=b ) and (c >=b) and (a >c )then     /* a>c>b */     
v:= a||'|'||c||'|'||b;
elsif (b >=a) and (a >=c)     then          /* b>a>c */
v := b||'|'||a||'|'||c;
elsif (b >=a) and (c >=a) and (b > c) then     /* b>c>a */
v:= b||'|'||c||'|'||a;          
elsif (c>=a) and (a>=b) then               /* c>a>b */
v:= c||'|'||a||'|'||b;          
else                               /* c>b>a */
v:= c||'|'||b||'|'||a;          
end if;
return v;
end;
create table tt(n1 number,n2 number,n3 number);
values are inserted like this
n1     n2     n3
3 2 1
3 1 2
2 1 3
2 3 1
1 2 3
1 3 2
select n1,n2,n3 , rec(n1,n2,n3) from tt;
output is like this
N1 N2 N3 RESULT
3 2 1 3|2|1
3 1 2 3|2|1
2 1 3 3|2|1
2 3 1 3|2|1
1 2 3 3|2|1
1 3 2 3|2|1
As you can see the result of the three columns coming thru a single column. what u need to do is just extract the required value to the required column using substr and instr functions.
Hope this helps you :-)
Please change the values and formatting as required if u want n1<n2<n3 , Pls make the necessary change in the
program .
Pls let me know if any difficulties
Rgds
Prakash Eranki
[email protected]
[email protected]