Update OrderID based on the Select Order By Results? - sql

Question

I am using SQLite 3. I have a table MyTable, as follows:
Create table mytable (ID as INTEGER, OrderID as INTEGER, a as INTGER, b as INTEGER);
Insert into mytable (ID, OrderID,a,b) values (1, 1,1,1);
Insert into mytable (ID, OrderID,a,b) values (1, 2,1,2);
Insert into mytable (ID, OrderID,a,b) values (2, 1,1,3);
Insert into mytable (ID, OrderID,a,b) values (2, 3,2,1);
Insert into mytable (ID, OrderID,a,b) values (3, 1,2,3);
Now if I using the following statement:
Select * from mytable ORDER BY a desc, b desc;
I will get all rows in a different order, as follows:
(3, 1, 2, 3);
(2, 3, 2, 1);
(2, 1, 1, 3);
(1, 2, 1, 2);
(1, 1, 1, 1);
Now I want to update the order ID to the sequence number of the rows appear in the above results, as follows:
(3, 1, 2, 3);
(2, 2, 2, 1);
(2, 3, 1, 3);
(1, 4, 1, 2);
(1, 5, 1, 1);
How to do so?

Answer 1

Try This :-
Select ROW_NUMBER() OVER (ORDER BY (SELECT 1 ) ) AS ordNo, * INTO #TempTable from
mytable ORDER BY a desc, b desc;
UPDATE mytable SET OrderID = ordNo FROM #TempTable WHERE mytable.ID
=#TempTable.ID AND mytable.a=#TempTable.a AND mytable.b=#TempTable.b

Answer 2

Assuming that the a and b values are unique:
update mytable t
set orderid = (select count(*)
from mytable t2
where t2.a > t.a or
(t2.a = t.a and t2.b >= t.b)
);

Answer 3

There is a column [rowid][1] responsible for every rowid
Most tables in a typical SQLite database schema are rowid tables.
Rowid tables are distinguished by the fact that they all have a unique, non-NULL, signed 64-bit integer rowid that is used as the access key for the data in the underlying B-tree storage engine.
Due to old SQLite version didn't support ROW_NUMBER window function, you can use a subquery in select to make it.
You can try to use correlated subquery and UPDATE by rowid.
Schema (SQLite v3.18)
Create table mytable (ID INT, OrderID INT, a INT, b INT);
Insert into mytable (ID, OrderID,a,b) values (1, 1,1,1);
Insert into mytable (ID, OrderID,a,b) values (1, 2,1,2);
Insert into mytable (ID, OrderID,a,b) values (2, 1,1,3);
Insert into mytable (ID, OrderID,a,b) values (2, 3,2,1);
Insert into mytable (ID, OrderID,a,b) values (3, 1,2,3);
update mytable
set orderid=
(
SELECT (select count(*)
from mytable tt
where tt.a > t1.a or
(tt.a = t1.a and tt.b >= t1.b)) rn
FROM mytable t1
where mytable.rowid=t1.rowid
);
Query #1
SELECT * FROM mytable order by OrderID;
| ID | OrderID | a | b |
| --- | ------- | --- | --- |
| 3 | 1 | 2 | 3 |
| 2 | 2 | 2 | 1 |
| 2 | 3 | 1 | 3 |
| 1 | 4 | 1 | 2 |
| 1 | 5 | 1 | 1 |
View on DB Fiddle