SQL IS NOT NULL.

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SQL IS NOT NULL Explanation

Understanding the SQL IS NOT NULL Condition

The IS NOT NULL condition in SQL is used to check for non-null values in a specified column. It helps in filtering the data by excluding rows where the column's value is NULL.

Examples

Consider a database table named Employees with the following columns:

  • Id - Employee's ID
  • Name - Employee's Name
  • Department - Department where the employee works
  • Email - Employee's Email Address

To select all employees who have an email address (i.e., where the email address is not null), you would use the following SQL query:

SELECT * FROM Employees WHERE Email IS NOT NULL;

This query returns all records from the Employees table where the Email column does not contain NULL values.

Combining Conditions

You can combine IS NOT NULL with other conditions to make more specific queries. For example, to find employees who are in the 'IT' department and have an email address, you might write:

SELECT * FROM Employees WHERE Department = 'IT' AND Email IS NOT NULL;

Note: It's crucial to use IS NOT NULL wisely, especially in databases where NULL values have significant meaning.

Common Uses of IS NOT NULL

The IS NOT NULL condition is particularly useful for ensuring that operations like concatenation, calculations, or functions that do not handle NULL appropriately are performed only on rows with valid data.

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