When to use the not exists operator in Oracle?

The NOT EXISTS operator returns true if the subquery returns no row. Otherwise, it returns false. Note that the NOT EXISTS operator returns false if the subquery returns any rows with a NULL value. To archive the customers who have no order, you use the following statement:

Why does ” grant select to role ” not allow members of role?

SELECT * FROM Table_1; SELECT * FROM Table_1 * ERROR at line 1: ORA-00942: table or view does not exist The role you created is password protected. Therefore it is not enabled by default, when alice logs in. You need to use the fully-qualified name of the table, as Alice does not own the table.

Why does select select…not allow members of role?

I missed to include the schema name in SELECT * FROM Table_1; command. However, even after adding the schema name as shown below, still the error comes. Unfortunately, this does not seem to solve the problem either. ALTER SESSION SET current_schema = ADMIN; Session altered.

How to fix ” grant select to role ” in Oracle?

When Alice runs the query Oracle will look in the current schema to see if there is an object named table_1. Since there is no such object, it throws an error. You can fix that by telling Oracle what schema the object resides in by qualiying the table name Alternately, you can create a synonym (public or private) that provides the mapping.

When to use not exists and not in?

In conclusion, the NOT EXISTS and NOT IN behave differently when there are null values involved. In this tutorial, you have learned how to use the Oracle NOT EXISTS operator to subtract one set of data from another.

How does null affect the result of not exist?

In contrast, NULL does not affect the result of the NOT EXIST operator because the NOT EXISTS operator solely checks the existence of rows in the subquery: In conclusion, the NOT EXISTS and NOT IN behave differently when there are null values involved.

When to use not exists in a subquery?

We often use the NOT EXISTS operator with a subquery to subtract one set of data from another. Consider the following statement that uses the NOT EXISTS operator: SELECT * FROM table_name WHERE NOT EXISTS (subquery); The NOT EXISTS operator returns true if the subquery returns no row.