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SQL for beginners

Negating conditions with NOT #

The NOT keyword flips a condition: rows that used to match are excluded, and rows that used to fail now match.

Syntax #

SELECT
    column_name
FROM
    table_name
WHERE
    NOT condition;

Example #

Instead of listing every category we do want, we can ask for every product that is not in the 'Office' category:

SELECT
    *
FROM
    products
WHERE
    NOT category = 'Office';

Result:

+----+-------------------+-------------+-------+
| id |       name        |  category   | price |
+----+-------------------+-------------+-------+
| 1  |  Wireless Mouse    | Electronics | 19.99 |
| 2  | Bluetooth Speaker  | Electronics | 45.5  |
| 3  |     Yoga Mat       |   Fitness   | 25.0  |
| 4  |   Running Shoes    |   Fitness   | 60.0  |
| 5  |    Coffee Mug      |    Home     |  8.5  |
| 6  |    Desk Lamp       |    Home     | 22.0  |
+----+-------------------+-------------+-------+

Notebook and Backpack, the two 'Office' products, are left out. NOT can be placed in front of any condition, including ones that use AND, OR, or the operators from earlier lessons.

Exercise #

Write a query that retrieves all columns from the products table, keeping only the rows where category is not 'Office'.

  • The result has a category column.
  • The result contains exactly the rows where category is not 'Office', and no others.
Solution 
SELECT
    *
FROM
    products
WHERE
    NOT category = 'Office';
Output will be displayed here