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NULL VALUES

A field with a NULL value is a field with no value. If a field in a table is optional, it is possible to insert a new record or update a record without adding a value to this field. Then, the field will be saved with a NULL values.

A NULL value is different from a zero value or a field that contains spaces. A field with a NULL value is one that has been left blank during record creation.

We cant compare null values with comparisions operator, so we use IS NULL and IS NOT NULL.

IS NULL and IS NOT NULL SYNTAX

• FOR IS NULL:

  SELECT column_names
  FROM table_name
  WHERE column_name IS NULL;
  

• FOR IS NOT NULL

  SELECT column_names
  FROM table_name
  WHERE column_name IS NOT NULL;
  

EXAMPLE

Suppose there is a Table name as “CustomerComplaint” having CustomerID, CustomerName, ProductName Issue, City, PostalCode and Country as columns.

• List all customers with a NULL value in the “Address” field:

  SELECT CustomerId, CustomerName, Address
  FROM CustomerComplaint
  WHERE Address IS NULL;
  

• Lists all customers with a value in the “Address” field:

  SELECT CustomerID, CustomerName, Address
  FROM CustomerComplaint
  WHERE Address IS NOT NULL;
  

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