NULL values

Author: utkarsh-1602

database-queries/MYSQL/NULL/Readme.md

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+# SQL 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` value.
+- It is not possible to test for NULL values with comparison operators, such as =, <, or <>.
+- We will have to use the `IS NULL` and IS `NOT NULL` operators instead.
+
+**IS NULL Syntax**:
+
+        SELECT column_names
+        FROM table_name
+        WHERE column_name IS NULL;
+
+
+**IS NOT NULL Syntax**:
+
+        SELECT column_names
+        FROM table_name
+        WHERE column_name IS NOT NULL;
+
+
+## CUSTOMERS
+
+| CustomerID | CustomerName       | ContactName     | Address            | City       | PostalCode | Country |
+|------------|--------------------|-----------------|--------------------|------------|------------|---------|
+| 1          | Company A          | John Doe        | 123 Main Street    | New York   | 10001      | USA     |
+| 2          | Company B          | Jane Smith      | 456 Oak Avenue     | Los Angeles| 90001      | USA     |
+| 3          | Company C          | Michael Johnson | 789 Elm Drive      | Chicago    | 60601      | USA     |
+| 4          | Company D          | Sarah Brown     | 101 Pine Road      | Houston    | 77001      | USA     |
+| 5          | Company E          | Sarah Jaden     |                    | barcelona  | 77031      | SPAIN   |
+
+
+### Q1
+From the `CUSTOMERS` Table, lists all customers with a NULL value in the "Address" field.
+
+```sql
+SELECT * FROM CUSTOMERS WHERE Address IS NULL; 
+```
+
+### Q2
+From the `CUSTOMERS` Table,  lists all customers with a value in the "Address" field:
+
+```sql
+SELECT * FROM CUSTOMERS WHERE Address IS NOT NULL; 
+```