What do you mean by NOT NULL? When will you use it?
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Answer / s
NOT NULL disallows nulls for the column. Primary Key must
be defined as NOT NULL or any key that you do not want to
have NULLS, becaue the default is that any column can
contain NULLs
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Answer / andank
NOT NULL is the keyword used define columns, when create a
table. When you specify NOT NULL to a column, that column
can not hold NULL values.
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Answer / s
CREATE UNIQUE WHERE NOT NULL INDEX index1
ON table(column);
WHERE NOT NULL ensures that non-null values are unique.
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