EXPERT RESPONSE
This requires the ALTER TABLE statement.
alter
table department
add column dept_location
integer not null default 0
The ALTER TABLE statement syntax may vary slightly from one database
system to another. Check your specific product manual.
One interesting point about adding a column is that it
cannot be declared NOT NULL unless it also has a DEFAULT value.
During the execution of the ALTER statement, every row will have to
be updated to add the new column. Thus, a value needs to be
assigned by the ALTER statement.
(If NULL is specified, a DEFAULT
may or may not be allowed by your particular database system.
If NULL is specified and DEFAULT is specified, it will be a little
trickier to insert a NULL. Note that this
nuance
is a rarity; DEFAULT doesn't make much sense for a NULL column.)
So if we add a new NOT NULL column with a DEFAULT value, the default will
be applied to all existing rows. But we can then ALTER the table again, to
change the column to NULL, with no DEFAULT, which means
that NULLs are now valid. Existing rows would be left alone. Again, the
specific ALTER TABLE syntax to change an existing column will
vary from one database system to another.
Check your specific product manual.
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