In SQL Server, ISNULL function is commonly used to populate a value for null columns. In Teradata, there is no ISNULL function but COALESCE and CASE WHEN can be used as alternatives.
Use COALESCE function
SELECT COALESCE(NULL,'ABC','CDE');
Result:
ABC
Apply to a column or expression
SELECT COALESCE(Col1, Col2,'DEFAULT') FROM DatabaseName.TableName;
Use CASE WHEN statement
SELECT CASE WHEN Col IS NULL THEN 'DEFAULT' ELSE Col END FROM DatabaseName.TableName;
Remember to change database, table and column names accordingly.