nested if , and how to trigger....

On Sun, 6 May 2001, Muhammad Rusydi wrote:

Hi,
can we do nested if in function ? would you give me some example?

In what context? In plpgsql, you can nest if's pretty normally:
create function f() returns int4 as '
begin
if (1=1) then
if (1=0) then
raise exception ''1=0'';
else
raise notice ''1!=0'';
end if;
else
raise exception ''1!=1'';
end if;
return 0;
end;' language 'plpgsql';

second, if i've create table like this:

create table tb (
code varchar(4),
classes varchar(6),
lecture varchar(4),
th int2,
day varchar(1),
hr varchar(1),
room varchar(4),
primary key (code,kl,ds));

code,kl,ds? What are kl and
ds?

my questions is how to prevent this record to be insert:
code classes lecture th day hr room
K021 1tip01 1011 5 1 1 1111
K022 1tip01 1011 5 1 1 1111

or :
code classes lecture th day hr room
K021 1tip01 1011 5 1 1 1111
K021 1tip01 1012 5 1 1 1111

If code or lecture must always be unique, then use a unique
constraint. If you can have duplicate codes if and only
if the lecture is the same and you can have duplicate lectures
if and only if the code is the same, you'll probably need
to do a before insert/update trigger that checks for you
(and you'll need to lock the table i think so that you
can't have two transactions inserting inconsistant data
that the other can't see due to it not being committed)

I think the question was whether a function can be called from within a
function. I sure hope so, although I don't know...

Ian

Stephan Szabo wrote:

Hi,

create table tb (
code varchar(4),
classes varchar(6),
lecture varchar(4),
th int2,
day varchar(1),
hr varchar(1),
room varchar(4),
primary key (code,kl,ds));

code,kl,ds? What are kl and
ds?

sorry, it should be code,classes,and lecture

my questions is how to prevent this record to be insert:
code classes lecture th day hr room
K021 1tip01 1011 5 1 1 1111
K022 1tip01 1011 5 1 1 1111

or :
code classes lecture th day hr room
K021 1tip01 1011 5 1 1 1111
K021 1tip01 1012 5 1 1 1111

code is for the subject that lecture teach on the class
what i really want to do is how to prevent:
1. different subject will not be give at same time (day and hr), same room
2. different lectures with same subject will not be at same time and room
too
3. but one lecture can teach same subject in different classes at same time
and room
TIA
Didi