The end result is ID 1 previously has priority 19938 should now have priority 38984. And ID 48 previously has priority 38984 should now have priority 19938.

What happens when that neighbouring row has been deleted? – What do you do when there is several numbers between?

Is there no order by asc / desc trick that can be used here?

Just in case you\’re curious:
For a categorized faq system I created the following table along with a couple of other columns:

id | parent | sortorder | content
—-+——–+———–+————————
1 | 0 | 1 | Category 1
—-+——–+———–+————————
2 | 1 | 1 | Category 1, subitem 1
—-+——–+———–+————————
3 | 1 | 2 | Category 1, subitem 2
—-+——–+———–+————————
4 | 1 | 3 | Category 1, subitem 3
—-+——–+———–+————————
5 | 0 | 2 | Category 2
—-+——–+———–+————————
6 | 5 | 1 | Category 2, subitem 1
—-+——–+———–+————————

Guess, you get the idea.
Now, in the backend, I wanted to implement an option to move items up and down. Modifying the query from here, I came up with this:

UPDATE $table AS hc1 JOIN $table AS hc2 ON ( hc1.id = $id AND hc2.sortorder = hc1.sortorder+1 AND hc2.parent = hc1.parent ) SET hc1.sortorder = hc2.sortorder, hc2.sortorder = hc1.sortorder;

$table is (obviously) the table name, while $id is the ID of the item you want to move. The above query moves the item with $id down. For the other way around, change the + to a -.
I just wanted to share that.

Can any tell me how can i swap “Take one bread to Wash hand” and “Wash hand to Take one bread” in Above table.

01.UPDATE
02. rules
03.SET
04. priority = rule1.priority
05.FROM
06. rules AS rule1
07.WHERE
08. rules.rule_id IN (1,4)
09. AND rule1.rule_id IN (1,4)
10. AND rules.rule_id <> rule1.rule_id
11.;

CREATE TABLE rules (
rule_id serial PRIMARY KEY,
rule_name varchar(255) NOT NULL,
priority integer
) ;

the without oids can be left out since its the default behavior for newer versions.

update rules
set priority = rule1.priority
from rules rule1
where rules.rule_id in (1, 4)
and rule1.rule_id + rules.rule_id = 1 + 4;