Menu
Amazon Redshift
Database Developer Guide (API Version 2012-12-01)

NVL2 Expression

Returns one of two values based on whether a specified expression evaluates to NULL or NOT NULL.

Syntax

NVL2 ( expression, not_null_return_value, null_return_value )

Arguments

expression

An expression, such as a column name, to be evaluated for null status.

not_null_return_value

The value returned if expression evaluates to NOT NULL. The not_null_return_value value must either have the same data type as expression or be implicitly convertible to that data type.

null_return_value

The value returned if expression evaluates to NULL. The null_return_value value must either have the same data type as expression or be implicitly convertible to that data type.

Return Type

The NVL2 return type is determined as follows:

  • If either not_null_return_value or null_return_value is null, the data type of the not-null expression is returned.

If both not_null_return_value and null_return_value are not null:

  • If not_null_return_value and null_return_value have the same data type, that data type is returned.

  • If not_null_return_value and null_return_value have different numeric data types, the smallest compatible numeric data type is returned.

  • If not_null_return_value and null_return_value have different datetime data types, a timestamp data type is returned.

  • If not_null_return_value and null_return_value have different character data types, the data type of not_null_return_value is returned.

  • If not_null_return_value and null_return_value have mixed numeric and non-numeric data types, the data type of not_null_return_value is returned.

Important

In the last two cases where the data type of not_null_return_value is returned, null_return_value is implicitly cast to that data type. If the data types are incompatible, the function fails.

Usage Notes

DECODE Expression can be used in a similar way to NVL2 when the expression and search parameters are both null. The difference is that for DECODE, the return will have both the value and the data type of the result parameter. In contrast, for NVL2, the return will have the value of either the not_null_return_value or null_return_value parameter, whichever is selected by the function, but will have the data type of not_null_return_value.

For example, assuming column1 is NULL, the following queries will return the same value. However, the DECODE return value data type will be INTEGER and the NVL2 return value data type will be VARCHAR.

select decode(column1, null, 1234, '2345'); select nvl2(column1, '2345', 1234);

Example

The following example modifies some sample data, then evaluates two fields to provide appropriate contact information for users:

update users set email = null where firstname = 'Aphrodite' and lastname = 'Acevedo'; select (firstname + ' ' + lastname) as name, nvl2(email, email, phone) AS contact_info from users where state = 'WA' and lastname like 'A%' order by lastname, firstname; name contact_info --------------------+------------------------------------------- Aphrodite Acevedo (906) 632-4407 Caldwell Acevedo Nunc.sollicitudin@Duisac.ca Quinn Adams vel@adipiscingligulaAenean.com Kamal Aguilar quis@vulputaterisusa.com Samson Alexander hendrerit.neque@indolorFusce.ca Hall Alford ac.mattis@vitaediamProin.edu Lane Allen et.netus@risusDonec.org Xander Allison ac.facilisis.facilisis@Infaucibus.com Amaya Alvarado dui.nec.tempus@eudui.edu Vera Alvarez at.arcu.Vestibulum@pellentesque.edu Yetta Anthony enim.sit@risus.org Violet Arnold ad.litora@at.com August Ashley consectetuer.euismod@Phasellus.com Karyn Austin ipsum.primis.in@Maurisblanditenim.org Lucas Ayers at@elitpretiumet.com