human
Considering the provided database schema and associated query, produce SQL code to retrieve the answer to the query. 
###Database Schema: No. in series, No. in season, Title, Directed by, Written by, Original air date, Production code
###Question: The episode with the original air date January 6, 1999, has what production code?
gpt
SELECT Production code FROM table WHERE Original air date = January 6, 1999