SQL Reverse entire column - mysql

Question

is there a way to reverse an entire column?
Example:
ID ColX ColY ColZ
0 001 010 100
1 002 020 200
2 003 030 300
shall be:
ID ColX ColY ColZ
0 003 030 300
1 002 020 200
2 001 010 100
So the Column ID shall be reversed, the record with the last ID shall be the first, the second last the second first and so far.
The newest value has ID = 0 and the oldest ID = n, and this must be exactly reversed, else I cannot insert new records.

Answer 1

You can do it using variables:
SELECT t2.ID, ColX, ColY, ColZ
FROM (SELECT ID, ColX, ColY, ColZ,
#row_number := #row_number + 1 AS rn
FROM mytable
CROSS JOIN (SELECT #row_number := 0) AS var
ORDER BY ID) AS t1
INNER JOIN (
SELECT ID, #rn := #rn + 1 AS rn
FROM mytable
CROSS JOIN (SELECT #rn := 0) AS var
ORDER BY ID DESC) AS t2
ON t1.rn = t2.rn
ORDER BY t2.ID
Demo here
If you want to UPDATE then you can use the above query in an UPDATE statement like this:
UPDATE mytable AS t
INNER JOIN(
SELECT ID, ColX, ColY, ColZ,
#row_number := #row_number + 1 AS rn
FROM mytable
CROSS JOIN (SELECT #row_number := 0) AS var
ORDER BY ID) AS t1 ON t.ID = t1.ID
INNER JOIN (
SELECT ID, #rn := #rn + 1 AS rn
FROM mytable
CROSS JOIN (SELECT #rn := 0) AS var
ORDER BY ID DESC) AS t2 ON t1.rn = t2.rn
SET t.ID = t2.ID
Demo here
The above will work irrespective of the values of ID column.

Answer 2

If you don't have gaps in your ID, then you can use this select query:
SELECT
max_id-ID AS ID,
ColX,
ColY,
ColZ
FROM
mytable CROSS JOIN (SELECT MAX(ID) AS max_id FROM mytable) m
ORDER BY
ID
or this update query (but it will work only if ID is not a primary key):
UPDATE
mytable m1 CROSS JOIN (SELECT MAX(ID) as max_id FROM mytable) m
SET
m1.ID = m.max_id - m1.ID
if it's a primary key you could use this:
UPDATE
mytable m1 CROSS JOIN (SELECT MAX(ID) as max_id FROM mytable) m
INNER JOIN mytable m2 ON m1.ID = m.max_id - m2.ID
SET
m1.ColX = m2.ColX,
m1.ColY = m2.ColY,
m1.ColZ = m2.ColZ
(please see it here)
but if your ID column has gaps (e.g. 0, 1, 2, 5, 6) you need a different approach.

Answer 3

SELECT
#x - t.id AS new_id,
t.*
FROM tab t,
( SELECT #x:= max(id+1) FROM tab ) m;
MariaDB [tmp]> SELECT
-> #x - t.id AS new_id,
-> t.*
-> FROM tab t,
-> ( SELECT #x:= max(id+1) FROM tab ) m;
+--------+----+--------+---------------------+
| new_id | id | action | date |
+--------+----+--------+---------------------+
| 7 | 1 | 2 | 2015-09-24 15:28:30 |
| 6 | 2 | 4 | 2015-09-24 15:29:26 |
| 5 | 3 | 2 | 2015-09-24 15:30:01 |
| 4 | 4 | 3 | 2015-09-24 15:30:55 |
| 3 | 5 | 1 | 2015-09-24 16:07:25 |
| 2 | 6 | 5 | 2015-09-24 16:10:25 |
| 1 | 7 | 4 | 2015-09-24 16:29:26 |
+--------+----+--------+---------------------+
7 rows in set (0.00 sec)