To modify the format of the result of a CASE expression, use CAST and specify the FORMAT clause.
Here is an example that uses CAST to change the format of the result of the CASE expression in the previous query.
SELECT i, ( CAST ((CASE WHEN i=1 THEN start_date WHEN i=2 THEN end_date END) AS DATE FORMAT 'M4BDD,BYYYY')) FROM duration ORDER BY 1;
For information on the default data type formats and the FORMAT phrase, see Teradata Vantage™ Data Types and Literals, B035-1143.