The difference between null and empty in oracle

NULL means missing or unknown, while null means an empty string or zero value. In a query, NULL is not equal to any value, and a null value is equal to a null value of the same type; the field must be explicitly defined to allow NULL, and null values ​​can exist in any field. Understanding the difference between NULL and empty is critical to writing accurate SQL queries and managing data.

The difference between NULL and empty in Oracle

NULL and empty in Oracle Although in some cases it can are used interchangeably, but they have different meanings in terms of internal representation and meaning.

NULL

• A value of NULL means that the field has no value.
• NULL indicates missing information or unknown, rather than a zero value or empty string.
• In a query, NULL is not equal to any other value, including other NULLs.
• Fields can contain NULL only if they are explicitly defined to allow NULL values.

Null

• The null value represents an empty string or zero value.
• The length of an empty string is 0, and the numeric value of a zero value is 0.
• In a query, empty strings are equal to other empty strings, and zero values ​​are equal to other zero values.
• Any field can contain null values, even if they are not explicitly defined to allow null values.

Difference

• Internal representation: NULL is a special value in the database that represents a missing or unknown value, while empty is Empty string or zero value.
• Query behavior: NULL is not equal to any other value, and a null value is equal to other null values ​​of the same type.
• Data integrity: Fields that allow NULL must be explicitly defined to ensure data integrity. And null values ​​can exist in any field, even if the field is not defined to allow null values.

Example

• A NULL value for the name field indicates that the individual's name is unknown.
• age The value of the field is an empty string indicating that the age of the individual is unknown.
• salary A value of 0 in the field indicates that the individual’s salary is 0.

Understanding the difference between NULL and empty is critical to writing accurate SQL queries and managing data in your database.

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