Usage of nvl in oracle

The NVL function in Oracle is used to replace the value with NULL. The syntax is NVL(value, default_value). Usage includes: checking and replacing NULL with default value; avoiding calculation and aggregation errors; ensuring database integrity.

Usage of NVL function in Oracle

The NVL function is used in Oracle to replace NULL values ​​to specify default values. . It takes two parameters:

• First parameter: the value to check.
• Second parameter: If the first parameter is NULL, the default value returned.

Syntax:

<code>NVL(value, default_value)</code>

Example:

Suppose there is a card named customers A table with the following columns:

• id (primary key)
• name
• email

If we want to replace "Unknown" with NULL for the email value, we can use the following query:

<code>SELECT id, name, NVL(email, 'Unknown') AS email
FROM customers;</code>

Result:

id	name	email
1	John	john@email.com
2	Jane	jane@email. com
3	Bob	Unknown

## Usage advantages:

The NVL function is useful in the following situations:

Replacing a value with NULL when reporting or displaying.
• Avoid errors in calculations or aggregation operations.
• Ensure database integrity and prevent NULL values ​​from being inserted into non-null columns.

Note:

The default value can be any data type as long as it is compatible with the value being checked.
• If the first argument is not NULL, the NVL function will simply return that value.
• If the first parameter and the default value are both NULL, the NVL function will return NULL.

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