NULL means 'not having a value' : Null « Data Type « SQL / MySQL






  1. SQL / MySQL
  2. Data Type
  3. Null

NULL means 'not having a value'

   
  
/*
mysql> SELECT 0 IS NULL, 0 IS NOT NULL, '' IS NULL, '' IS NOT NULL;
+-----------+---------------+------------+----------------+
| 0 IS NULL | 0 IS NOT NULL | '' IS NULL | '' IS NOT NULL |
+-----------+---------------+------------+----------------+
|         0 |             1 |          0 |              1 |
+-----------+---------------+------------+----------------+
1 row in set (0.00 sec)


*/ 


SELECT 0 IS NULL, 0 IS NOT NULL, '' IS NULL, '' IS NOT NULL;








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