nvl2 function
Applies to: 
Databricks SQL Databricks Runtime
Returns expr2 if expr1 is not NULL, or expr3 otherwise. This function is a synonym for CASE WHEN expr1 IS NOT NULL expr2 ELSE expr3 END.
Syntax
nvl2(expr1, expr2, expr3)
Arguments
expr1: An expression of any type.expr2: An expression of any type.expr3: An expression that shares a least common type withexpr2.
Returns
The result is least common type of expr2 and expr3.
Special considerations apply to VARIANT types. See isnull function for details.
Examples
SQL
> SELECT nvl2(NULL, 2, 1);
1
> SELECT nvl2('spark', 2, 1);
2