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Today, the editor will share with you the relevant knowledge points about how to use null values in mysql. The content is detailed and the logic is clear. I believe most people still know too much about this knowledge, so share this article for your reference. I hope you can get something after reading this article. Let's take a look at it.

1. NULL is not 0 and cannot be compared. NULL can also be understood as an unknown placeholder.

2. The length of NULL is NULL, but it takes up space.

3. Null values cannot be operated by comparison algorithms, such as =, or.

For null values, IS NULL and IS NOT NULL must be used.

Example

Mysql > select * from test_class +-+ | class_id | class_name | +-+-+ | 1 | Class 1 | Class 2 | Class 2 | Class 3 | Class 3 | 4 | Class 4 | 5 | Grade 2 (1) Class | | 6 | Class (2) of the second year of junior high school | | 7 | Class (3) of the second year of junior high school | | 8 | Class 4 of the second year of junior high school | | 9 | Class 1 of the third year of junior high school | | 10 | Class 2 of the third year of junior high school | | 11 | Class 3 (3) | 12 | Class 4 | 13 | NULL | +-+- + 13 rows in set (0.00 sec) and above are all the contents of the article "how to use null values in mysql" Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.

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