Hi,
I am using SQLite 3.11. I create a table as follows:
CREATE TABLE MyTable (F1 INTEGER, F2
INTEGER, F3 INTEGER);
Then add the following records:
INSERT INTO MyTable (F1, F2, F3) Values (1,
2, 8);
INSERT INTO MyTable (F1, F2, F3) Values (1,
3, 9);
INSERT INTO MyTable (F1, F2, F3) Values (2,
4, 8);
INSERT INTO MyTable (F1, F2, F3) Values (2,
5, 2);
INSERT INTO MyTable (F1, F2, F3) Values (3,
6, 4);
INSERT INTO MyTable (F1, F2, F3) Values (3,
7, 8);
INSERT INTO MyTable (F1, F2, F3) Values (4,
2, 4);
INSERT INTO
MyTable (F1, F2, F3) Values (4, 2, 6);
Now if I want to select from MyTable, and sort the result based on F1
(ascendant), and for two records with same F1, then sort based on
F2(ascendant), then sort based on F3(ascendant) should I use the following
:
SELECT * FROM MyTable ORDER BY F1, F2, F3?
I check https://www.sqlite.org/lang_select.html#orderby and it said ?Rows
are first sorted based on the results of evaluating the left-most expression
in the ORDER BY list, then ties are broken by evaluating the second
left-most expression and so on.? So based on my understanding, my statement
is correct.
Moreover, since the sort will be performed frequently, to improve the
performance, I want to add a field F4, then update the table so that all the
records will have a unique F4 value which is the order sequence based on the
above order by clause, thus if I want to select again, I do not need to use
ORDER BY F1, F2, F3 any more, instead, I can use:
SELECT * FROM MyTable ORDER BY F4
Is that feasible? If yes, how do to that?
Thanks
