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SQL IS NOT NULL condition
The IS NOT NULL condition is used in SQL to check a value other than NULL. It returns TRUE if a non-zero value is found, otherwise it returns FALSE. It can be used in SELECT, INSERT, UPDATE or DELETE operator.
Syntax for IS NOT NULL condition in SQL
expression_id IS NOT NULL
where:
- expression_id – Expression to check the NOT NULL value.
Using IS NOT NULL with SELECT operator
When checking a value other than NULL, IS NOT NULL is the recommended comparison operator for use in SQL. Let us start with an example which shows how to use the IS NOT NULL condition in a SELECT sentence.
In this example, we have a product table with the following data:
| prod_id | prod_name | cat_id |
|---|---|---|
| 1 | Pear | 50 |
| 2 | Banana | 50 |
| 3 | Orange | 50 |
| 4 | Apple | 50 |
| 5 | Bread | 75 |
| 6 | Sliced Ham | 25 |
In this example, all records from the products table where custom_id does not contain a NULL value will be returned.
Using IS NOT NULL with UPDATE operator
Next let’s consider an example of using the IS NOT NULL condition in the UPDATE query.
In this example, we have a customer table with the following data:
| custom_id | f_name | l_name | fav_website |
|---|---|---|---|
| 4000 | Justin | Bieber | google.com |
| 5000 | Selena | Gomez | bing.com |
| 6000 | Mila | Kunis | yahoo.com |
| 7000 | Tom | Cruise | oracle.com |
| 8000 | Johnny | Depp | NULL |
| 9000 | Russell | Crowe | google.com |
Enter the following UPDATE request:
UPDATE customs
SET fav_website = 'google.com'.
WHERE fav_website IS NOT NULL;
5 records will be updated. Select the data from the table again:
SELECT *
FROM customs;
here are the results you should get:
| custom_id | f_name | l_name | fav_website |
|---|---|---|---|
| 4000 | Justin | Bieber | google.com |
| 5000 | Selena | Gomez | google.com |
| 6000 | Mila | Kunis | google.com |
| 7000 | Tom | Cruise | google.com |
| 8000 | Johnny | Depp | NULL |
| 9000 | Russell | Crowe | google.com |
In this example, all fav_website values in the customer table will be updated to google.com, where fav_website contains the value NULL. As you can see the values of fav_website field are updated all but one lines.
Using IS NOT NULL with DELETE operator
Next, let’s look at an example of using the IS NULL condition in the DELETE query.
In this example, we have a table of orders and the following data:
| ord_id | custom_id | ord_date |
|---|---|---|
| 1 | 7000 | 2019/06/18 |
| 2 | 5000 | 2019/06/18 |
| 3 | 8000 | 2019/06/19 |
| 4 | 4000 | 2019/06/20 |
| 5 | NULL | 2019/07/01 |
Enter the following DELETE request:
DELETE FROM ords
WHERE custom_id IS NOT NULL;
Four records will be deleted. Select the data from the order table again:
SELECT *
FROM ords;
Here are the results you’ll get:
| ord_id | custom_id | ord_date |
|---|---|---|
| 5 | NULL | 2019/07/01 |
In this example, all records from the order table where custom_id does not contain a NULL value will be deleted.
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