| Burton |
Posted: Mar 23, 2007 08:36:00 AM |
Total Post: 53
Joined: Dec, 2006
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Amigos:
When we change a column that already has data in it, and change it to NULL, what happens to the data that already exists in the column? is it set to NULL also, or is only the data that is inserted *after* we change the column set to NULL?
B |
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 Burton |
| Posted: Mar 23, 2007 10:00:02 AM |  |
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Total Post: 53
Joined: Dec, 2006
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OK - I answered this one myself by making a test table:
Using
update t set c = null;
will change the existing rows to null. This is an example of using the = operator with the NULL.
Cheers.
B
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| Rush |
| Posted: Mar 25, 2007 03:49:13 AM | |
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Total Post: 127
Joined: Jan, 2007
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hi Butron
you can set NULL OR NOT NULL but the property of null and not null will be applyed when the columns satisfy the rul
1) NOT NULL column set to null->alltheexisting data should be removed first.
2)NULL column set to not null->every rowof that column should haveany value.
thanks and regard
RUPESH
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| Burton |
| Posted: Mar 25, 2007 08:17:37 AM | |
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Total Post: 53
Joined: Dec, 2006
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Yes, I think the point here is that this is an example of using "=" NULL instead of IS NULL.
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