The NULL predicate combined with NOT manipulates rows that do not contain any null values in their table columns.

When NOT is not combined with the NULL predicate, the rows containing the null value become the target of manipulation.

Figure 2-27 shows a data search example using a NULL predicate with NOT. Here, form numbers, product codes, and the ordered quantities are searched from the order table for those in which customer codes have been set (non-null values).

Figure 2-27 Data search example using a NULL predicate with NOT