Probably because ...
Quote
3 rows in set (0.00 sec)
You removed and added
columns, not
rows!
Your table started out looking like this:
+-----------+-------+-------+-------+
| jobnumber | ord_y | ord_m | ord_s |
+-----------+-------+-------+-------+
| 123 | 2021 | 6 | 1 |
| 456 | 2021 | 6 | 2 |
| 789 | 2021 | 6 | 3 |
+-----------+-------+-------+-------+
Then you removed the jobnumber column:
alter table orderform
drop jobnumber;
+-------+-------+-------+
| ord_y | ord_m | ord_s |
+-------+-------+-------+
| 2021 | 6 | 1 |
| 2021 | 6 | 2 |
| 2021 | 6 | 3 |
+-------+-------+-------+
Then you added a column called jobnumber again.
alter table orderform
add jobnumber int(8) not null first ;
+-----------+-------+-------+-------+
| jobnumber | ord_y | ord_m | ord_s |
+-----------+-------+-------+-------+
| 0 | 2021 | 6 | 1 |
| 0 | 2021 | 6 | 2 |
| 0 | 2021 | 6 | 3 |
+-----------+-------+-------+-------+
None of the other data in any of the other columns was touched.
Now, that last bit
should have been to add a
derived column to work out the value of jobnumber based on the order's year, month and sequence, something like this:
alter table orderform
add jobnumber int(8) not null first
generated always as ( 10000 * ( 100 * ord_y + ord_m ) + ord_s );
+------------+-------+-------+-------+
| jobnumber | ord_y | ord_m | ord_s |
+------------+-------+-------+-------+
| 2021060001 | 2021 | 6 | 1 |
| 2021060002 | 2021 | 6 | 2 |
| 2021060003 | 2021 | 6 | 3 |
+------------+-------+-------+-------+
Regards, Phill W.