如何以相反的顺序更新字段到MYSQL表中的其他字段

Question

I have a table with fields like this

lev_1_id,lev_1_seq,lev_1_new_seq,lev_2_id,lev_2_seq,lev_2_new_seq

284e777e,1,null,b4dce5bb,1,null<br>
284e777e,1,null,dfd158ed,2,null<br>
284e777e,1,null,fedbf511,3,null<br>
0c7e0938,2,null,2333f431,1,null<br>
0c7e0938,2,null,808734fa,2,null<br>
0c7e0938,2,null,2504e0de,3,null<br>

And now I want to update the lev_1_new_seq and, lev_2_new_seq by reversing the values in lev_1_seq and lev_2_seq respectively.

After updating the fields, the table should look like this:

lev_1_id,lev_1_seq,lev_1_new_seq,lev_2_id,lev_2_seq,lev_2_new_seq

284e777e,1,2,b4dce5bb,1,3<br>
284e777e,1,2,dfd158ed,2,2<br>
284e777e,1,2,fedbf511,3,1<br>
0c7e0938,2,1,2333f431,1,3<br>
0c7e0938,2,1,808734fa,2,2<br>
0c7e0938,2,1,2504e0de,3,1<br>

can anyone help me with updating the fields?

Thanks in advance!

Answer 1

It appears that you should be able to calculate the "new" sequences by deducting the exiting sequences from the relevant maximums + 1.

eg the max(lev_1_seq) + 1 = 3, so for an existing value of 2: 3-2 = 1, for an existing value of 1: 3-1 = 2

UPDATE table1 tu
JOIN (
      SELECT
            t1.lev_1_id
          , m1.lev1maxseq
          , MAX(t1.lev_2_seq) + 1 lev2maxseq
      FROM table1 t1
            CROSS JOIN (
                  SELECT
                        MAX(lev_1_seq) + 1 lev1maxseq
                  FROM table1
            ) m1
      GROUP BY
            t1.lev_1_id
          , m1.lev1maxseq
      ) nv on tu.lev_1_id = nv.lev_1_id
SET
    tu.lev_1_new_seq = (nv.lev1maxseq - tu.lev_1_seq)
  , tu.lev_2_new_seq = (nv.lev2maxseq - tu.lev_2_seq)
;

see this sqlfiddle

results:

| lev_1_id | lev_1_seq | lev_1_new_seq | lev_2_id | lev_2_seq | lev_2_new_seq |
|----------|-----------|---------------|----------|-----------|---------------|
| 284e777e |         1 |             2 | b4dce5bb |         1 |             3 |
| 284e777e |         1 |             2 | dfd158ed |         2 |             2 |
| 284e777e |         1 |             2 | fedbf511 |         3 |             1 |
| 0c7e0938 |         2 |             1 | 2333f431 |         1 |             3 |
| 0c7e0938 |         2 |             1 | 808734fa |         2 |             2 |
| 0c7e0938 |         2 |             1 | 2504e0de |         3 |             1 |

Answer 2

This solution works if initial ordering was done by id. 2 - the column you updating, 1 - column that needs to be in reverse order, tmp - table, id - unique key, initial sorting column.

BEGIN
DECLARE p INT;
DECLARE v INT;
DECLARE n INT DEFAULT 0;
DECLARE i INT DEFAULT 0;
SELECT COUNT(*) FROM `tmp` INTO n;
SET i=0;
WHILE i<n DO 
  select `1` from `tmp` order by `id` desc limit i,1 into p;
  select `id` from `tmp` order by `id` limit i,1 into v;

  update `tmp` set `2` = p where `id` = v;
  SET i = i + 1;
END WHILE;
End

For your table: 1 = lev_1_seq, 2 = lev_1_new_seq, id = lev_1_id