The difference between null and empty values ​​in mysql

NULL represents an unknown and meaningless value, while a null value represents an unassigned or uninitialized value. The differences between the two are: semantic differences, database processing methods, query optimization impact, data integrity impact, which can be distinguished through the operators provided by MySQL.

The difference between NULL and null values ​​in MySQL

What is NULL?

NULL represents an unknown or meaningless value. It indicates that no valid value exists.

What is a null value?

A null value represents an unassigned or uninitialized value. It doesn't have to be NULL, but it might be.

Difference between NULL and null value

• Semantic difference: NULL indicates the complete absence of a value, while a null value may indicate a temporary Unknown or unassigned value.
• Database processing: MySQL treats NULL as a specific value, and null values ​​as missing or unknown values.
• Query Optimization: NULL can affect query optimization because it is a unique value, and a null value can contain various possible interpretations.
• Data integrity: NULL can be used to enhance data integrity and force certain fields to have values.

Example scenario:

• Customer name field: NULL means that the customer does not know the name or did not provide a name. A null value means the field has not been populated yet.
• Order date field: NULL means the order has not been placed yet. An empty value indicates that the order date has not yet been determined.

How to distinguish between NULL and empty values?

MySQL provides IS NULL and IS NOT NULL operators to check whether a value is NULL. Null values ​​cannot be detected using these operators.

Conclusion:

NULL and null values ​​are different concepts in MySQL. NULL means that no valid value exists, while an empty value means an unassigned or uninitialized value. Understanding their differences is critical to correctly interpreting and processing data.

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