How to add MySQL table column with a default value of another column of the existing row

Question

The current existing table looks like this:

id    number    amount    
1     123       30000.00
2     123       15000.00
3     321       45000.00
...   ...       ...
1000  567       75000.00

Now i would like add new column allocated_amount with the default value of the amount column in every existing row.

id    number    amount      allocated_amount  
1     123       30000.00    30000.00
2     123       15000.00    15000.00
3     321       45000.00    45000.00
...   ...       ...         ...
1000  567       75000.00    75000.00

It is possible? Im using MySQL Workbench GUI.

Answer 1

It is not possible as default column. You can write a trigger and do that or add virtual column in Mysql 5.7.

OR

alter table Tab1 add allocated_amount int;  -- Add column
update Tab1 set allocated_amount= amount;   -- Set the value

Or you could create a Virtual Column:

alter table Table1 
add allocated_amount integer GENERATED ALWAYS AS (amount) VIRTUAL;