What is the difference between nvl in oracle and nvl in hive

Oracle and Hive’s NVL functions are used to handle NULL values, but there are differences: NULL handling: Hive NVL can handle NULL replacement_value, but Oracle NVL cannot. Nested NULL checks: Hive NVL can check for NULL in nested expressions, while Oracle NVL cannot.

Differences between NVL functions in Oracle and Hive

The NVL functions are used to process both Oracle and Hive NULL value, but there are some differences between the two.

Oracle NVL

In Oracle, the NVL function has the following format:

<code class="sql">NVL(expression, replacement_value)</code>

• expression is to be checked The expression, if it is NULL, returns replacement_value.
• replacement_value is the value to be returned when expression is NULL.

Hive NVL

In Hive, the NVL function also has the following format:

<code class="sql">NVL(expression, replacement_value)</code>

Its parameters and functions are similar to the Oracle NVL function , but has some additional features:

• If replacement_value is also NULL, the Hive NVL function returns NULL.
• Hive NVL functions can handle nested NULL values, which means it can check nested expressions for NULL values.

Key Differences

The following are the key differences between Oracle and Hive NVL functions:

• NULL Handling : Hive NVL functions handle NULL replacement_value, while Oracle NVL functions do not.
• Nested NULL checks: Hive NVL functions can check nested expressions for NULL values, while Oracle NVL functions cannot.

Example

In Oracle, the following query returns "Unknown" because replacement_value is not NULL:

<code class="sql">SELECT NVL(NULL, 'Unknown');</code>

And in Hive, the same query returns NULL because replacement_value is NULL:

<code class="sql">SELECT NVL(NULL, NULL);</code>

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