Question

Which operator is used to compare NULL value in the table? Explain with syntax and examples.​

Answer 1

Answer:

The IS NULL operator is used to test for empty values (NULL values).

Answer 2

Answer:

The IS NULL operator is used to compare NULL values in a table. It is used to check if a column in a table has a NULL value or not.

Explanation:

The syntax for using the IS NULL operator is:

SELECT column_name FROM table_name WHERE column_name IS NULL;

Here, column_name is the name of the column that you want to check for NULL values and table_name is the name of the table.

Here is an example of using the IS NULL operator to check for NULL values in a table named "employees":

SELECT * FROM employees WHERE salary IS NULL;

This query selects all columns from the "employees" table where the "salary" column has a NULL value.

You can also use the IS NOT NULL operator to check if a column does not have a NULL value, the syntax is:

SELECT column_name FROM table_name WHERE column_name IS NOT NULL;

Here is an example of using the IS NOT NULL operator to check for NOT NULL values in a table named "employees":

SELECT * FROM employees WHERE salary IS NOT NULL;

This query selects all columns from the "employees" table where the "salary" column does not have a NULL value.

It's important to note that the NULL value is different from an empty string or zero value, NULL means that the value is not known or not applicable, whereas an empty string or a zero value means that the value is explicitly known to be empty or zero.

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