If you specify NOT NULL when you create a column and do not create a default for it, SAP ASE produces an error message whenever a user inserts a row without making an entry in that column.
When you drop a default for a NULL column, SAP ASE 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.
This table 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 |