Question

In a query, the search criteria REGION NOT = "CA" OR REGION NOT ="NV" will display?

1) An error message
2) All the rows in the table
3) Only the rows in which Region is equal to "CA" or "NV"
4) All the rows in the table except those in which Region is NULL
5) All the rows in the table except those in which the Region is "CA" or "NV"

Answer 1

The query will display all rows except those where Region is NULL, as the NOT EQUAL condition in SQL does not return rows where the column value is NULL.

Step-by-step explanation:

The query with the search criteria REGION NOT = "CA" OR REGION NOT ="NV" will display all the rows in the table except those where the Region is NULL. This is because logical conditions in queries are evaluated for each row, and in SQL, the NOT EQUAL condition will not return rows where the column has a NULL value.

Typically, in boolean logic, if we have a condition saying NOT X OR NOT Y, it means we are looking for anything that is either not X or not Y or both. However, in SQL, a NULL value does not satisfy any comparison condition (such as != or <>, which stands for NOT EQUAL), except for the IS NULL condition. So, if the Region is NULL, the given conditions will not include those rows, and they won't be displayed in the query result.

Therefore, the correct answer would be 4) All the rows in the table except those in which Region is NULL.