If you specify NOT NULL when you create a column and do not create a default for it, Adaptive Server produces an error message whenever anyone inserts a row and fails to make an entry in that column.
When you drop a default for a NULL column, Adaptive Server inserts NULL in that position each time you add rows without entering any value for that column. When you drop a default for a NOT NULL column, you get an error message when rows are added, without a value entered for that column.
Table 14-1 illustrates the relationship between the existence of a default and the definition of a column as NULL or NOT NULL.
Column definition |
User entry |
Result |
|---|---|---|
Null and default defined |
No value NULL value |
Default used NULL used |
Null defined, no default defined |
No value NULL value |
NULL used NULL used |
Not null, default defined |
No value NULL value |
Default used Error |
Not null, no default defined |
No value NULL value |
Error Error |
