nexval error duplicate key

I am getting the darnest error here

I think I narrowed it down

Problem:

In a simplified version of the program is the following, this is
completed in ColdFusion which I don't think is an issue

My understanding of SQL database is limited

I set up a table

field
id
name_insert

I basically want to add a name in the 'name_insert' field and let
'id' to incrementally increase automatically

An html was created with ONLY one field to add a name
An html was created to list the names and modify the name

I used the code something like the following:

CREATE TABLE name_table (
id SERIAL,
name_insert TEXT
);

Basically when the name is inserted it works fine

I check the table I get the following

for example DATA 1
1 john
2 mary
3 josephine
4 ron

Then here is the issue

I modify 2 mary to 2 jane
the database modified to

DATA 2

1 john
3 josephine
4 ron
2 jane

When I use postgresql admin I get DATA 2

the number is OUT of order

NOW when I add a new value

it give me an error that states:

--------------------------------------------------------

Error Occurred While Processing Request

Error Diagnostic Information

ODBC Error Code = 08S01 (Communication link failure)

Error while executing the query; ERROR: Cannot insert a duplicate key
into unique index name_pkey

The error occurred while processing an element with a general
identifier of (CFQUERY), occupying document position (1:61) to
(1:110).
--------------------------------------------------------

I only put the relavent error above

It seems when the nextval is used here the sql thinks the last value
is '3' because the last value is '2 jane' so it seems logical to get
'3' as the next value.

Additional information:

If I move the highest value '4 ron' by editing it, just as I edited
'2 jane' then I get '4 ronald'

DATA 3

1 john
3 josephine
2 jane
4 ronald

Now when I add a new record like 'sam' no error

DATA 3

1 john
3 josephine
2 jane
4 ronald
5 sam

so now it works

What's the deal?

doesn't 'nexval' find the greatest value? or does it seem to get the
last value in the list

so I am thinking the best way is to sort the table OR I am thinking
that when I find the next value it does a sort then find the last
value

so I am stuck any ideas of what I can do?

Ron Sattar

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