On 27-2-2018 04:42, hugo.larson@... [firebird-support] wrote:

> Does null values take up disk space?
>
> If I have a table with 4 VARCHAR columns and I add 4 more does the table
> need double space even if the new columns are null?

I recently answered this question on dba.stackexchange.com:
https://dba.stackexchange.com/questions/198260/firebird-table-and-null-data

In short, adding a new column will not affect existing records (until
you update them). A new column will affect storage, but this will be
just a few bytes per column if the value is null due to the applied RLE
compression. As far as I know, for most datatypes 2 bytes, and for
char/varchar possibly multiples of two bytes depending on the column
(byte) length.

Mark
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Mark Rotteveel