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# IS NOT DISTINCT FROM Operator

## **Overview**

The `IS NOT DISTINCT FROM` operator is a counterpart to `IS DISTINCT FROM`.

It compares two values, treating them as equal even when they are both `NULL`. This operator returns `TRUE` if the two values are the same, including the case where both values are `NULL` and `FALSE` if they are different.

## **Syntax**

The syntax for the operator is as follows:

```sql theme={null}
value1 IS NOT DISTINCT FROM value2
```

Where:

* `value1` is the first value for comparison.
* `value2` is the second value for comparison.

## Examples

### Case #1: Basic Usage

Consider the following example where we compare two values:

**Example 1**

```sql theme={null}
SELECT 45 IS NOT DISTINCT FROM 45 AS "Result";  
```

The above query will return the following output:

```sql theme={null}
 Result 
--------
 t
```

**Example 2**

```sql theme={null}
SELECT 60 IS NOT DISTINCT FROM 30 AS "Result";    
```

The above query will return the following output:

```sql theme={null}
 Result 
--------
 f
```

**Example 3**

```sql theme={null}
SELECT NULL IS NOT DISTINCT FROM NULL AS "Result";
```

The above query will return the following output:

```sql theme={null}
 Result 
--------
 t
```

### Case #2: Comparing NULL Values

In this example, we'll compare NULL values using the IS NOT DISTINCT FROM operator:

**Example 1**

```sql theme={null}
SELECT NULL IS NOT DISTINCT FROM 80 AS "Result";   
```

The above query will return the following output:

```sql theme={null}
 Result 
--------
 f
```

**Example 2**

```sql theme={null}
SELECT 5 IS NOT DISTINCT FROM NULL AS "Result";
```

The above query will return the following output:

```sql theme={null}
 Result 
--------
 f
```

### Case #3: Analyzing Data Completeness

Suppose we have a table named customer\_contacts that stores customer contact information. 

```sql theme={null}
CREATE TABLE customer_contacts (
  customer_id INT,
  email TEXT,
  phone TEXT
);

INSERT INTO customer_contacts VALUES
(101, 'john@example.com', NULL),
(102, NULL, '+1234567890'),
(103, 'jane@example.com', '+9876543210'),
(104, NULL, NULL),
(105, 'alex@example.com', '+5555555555');
```

Our objective is to retrieve records from this table where an email address or a phone number is available for contacting the customers.

```sql theme={null}
SELECT *
FROM customer_contacts
WHERE email IS NOT DISTINCT FROM phone;
```

In this query, we retrieve all rows from the `customer_contacts table` where the email and phone are NULL. We can conclude that the customer with `customer_id 104` has no phone number or email address.

```sql theme={null}
 customer_id | email | phone 
-------------+-------+-------
         104 |       | 
```