EllisLab/CodeIgniter — pull request #3198 by ivantcholakov (2014-08-21 17:14:18+00:00)
Title: Query builder: IS NOT NULL support implementation, see #3194

```php
$sql = $this->db
->from('products')
->where('category_id <>', NULL)
->get_compiled_select();

echo $sql;
```
The expected result is:
```sql
SELECT *
FROM `products`
WHERE `category_id` IS NOT NULL
```