sql - UPDATE with ORDER BY

Question

Need to "tie" UPDATE with ORDER BY. I'm trying to use cursors, but get the error:

cursor "cursupd" doesn't specify a line,
SQL state: 24000

Code:

BEGIN;
    DECLARE cursUpd CURSOR FOR SELECT * FROM "table" WHERE "field" = 5760 AND "sequence" >= 0 AND "sequence" < 9 ORDER BY "sequence" DESC;
    UPDATE "table" SET "sequence" = "sequence" + 2 WHERE CURRENT OF cursUpd;
    CLOSE cursUpd;
COMMIT;

How to do it correctly?

UPDATE 1

Without cursor, when I do like this:

UPDATE "CableLinePoint" AS "t"
SET "sequence" = t."sequence" + 2
from (
    select max("sequence") "sequence", "id"
    from "CableLinePoint"
    where
        "CableLine" = 5760
    group by "id"
    ORDER BY "sequence" DESC
) "s"
where "t"."id" = "s"."id" and "t"."sequence" = "s"."sequence"

I get the unique error. So, need to update from the end rather than from the beginning.

UPDATE 2

Table:

id|CableLine|sequence
10|    2    |    1
11|    2    |    2
12|    2    |    3
13|    2    |    4
14|    2    |    5

Need to update (increase) the field "sequence". "sequence" have "index" type, so cannot be done:

UPDATE "table" SET "sequence" = "sequence" + 1 WHERE "CableLine" = 2

When "sequence" in the row with id = 10 is incremented by 1 I receive an error that another row with "sequence" = 2 already exists.

Answer 1

UPDATE with ORDER BY:

UPDATE thetable 
  SET columntoupdate=yourvalue 
 FROM (SELECT rowid, 'thevalue' AS yourvalue 
         FROM thetable 
        ORDER BY rowid
      ) AS t1 
WHERE thetable.rowid=t1.rowid;

UPDATE order is still random (I guess), but the values supplied to UPDATE command are matched by thetable.rowid=t1.rowid condition. So what I am doing is, first selecting the 'updated' table in memory, it's named t1 in the code above, and then making my physical table to look same as t1. And the update order does not matter anymore.

As for true ordered UPDATE, I don't think it could be useful to anyone.