Question

I’m working on the first giant update to my website. It has an existing table for posts. If I add on two columns to the table, will I be able to import the old data to the updated table?

EDIT: I meant columns. Whoops.

Answer 1

You mean two columns? If they are nullable then you should be able to import your old data which doesn’t contain these columns. You’ll just need to write your insert statement carefully by making sure to specify the exact columns you are inserting into. This is a good practice and should be done anyway (thanks Bruno for the tip).

Example:

INSERT INTO table1 (Col1, Col2, Col3)
SELECT Col1, Col2, Col3
FROM sourceTable

Instead of

INSERT INTO table1
SELECT *
FROM sourceTable

If the two new columns are not nullable then you can you try appending some dummy data using literals just to get the insert to work.

Example:

INSERT INTO table1 (Col1, Col2, Col3, NewCol1, NewCol2)
SELECT Col1, Col2, Col3, '', ''
FROM oldDataTable

Or you could create a default constraint which will work just as well.