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Message Posted: Thu, 19 May 2016 @ 20:14:40 GMT

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I think that even if there is a null-bit available, each row has to be accessed.

Even if the default is NULL for the new column then I think that we have to go through every row to set the null bit 'on' to indicate that the new column in that row contains null. I'm assuming here that a '1' means the column contains null whilst '0' means it does not contain null. Certainly that is how nulls are identified on the client side (which I accept may be different from how it is done in the dbms).

Off the top of my head I can't come up with a scenario where adding a new column (or removing one) does NOT do a full table scan.

Cheers,

Dave

Ward Analytics Ltd - Information in motion (www.ward-analytics.com)

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