What does nvl mean in oracle

The NVL function in Oracle is used to handle null values. It checks whether expr1 is null and returns expr2 if it is null, otherwise it returns expr1. Advantages include preventing errors, returning user-friendly values, and simplifying queries. The limitation is that it can only handle a single value and the replacement value must be compatible with expr1's data type.

NVL function in Oracle

NVL is a function in Oracle that is used to handle null values. It takes two parameters:

• #expr1: The value to check for null.
• expr2: The value returned if expr1 is empty.

How it works

The NVL function checks whether expr1 is NULL. If expr1 is NULL, the function returns the value of expr2. Otherwise, the function returns the value of expr1.

Syntax

<code class="oracle">NVL(expr1, expr2)</code>

Example

The following example checks whether the LAST_NAME column is empty:

<code class="oracle">SELECT NVL(LAST_NAME, 'Unknown') FROM employees;</code>

if LAST_NAME is NULL, then it will return 'Unknown'. Otherwise, it returns the actual last name.

Advantages

Using NVL functions has the following advantages:

• It prevents operations on NULL values, thus avoiding errors.
• It can return user-friendly values ​​instead of displaying NULL.
• It simplifies queries because there is no need to use IFNULL or CASE statements to handle null values.

Limitations

The limitations of the NVL function are:

• It can only process a single value, not the entire expression Mode.
• The replacement value it returns must be compatible with the data type of expr1.

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