Unanswered: Retreive the previous date period,prior year end in table
I have a Date table in the database which has columns Date_id, yr_num, month_num, week_num. The Date Id has the values 2013-01-04, 2013-01-11, 2013-01-18, 2013-01-25, 2013-01-31, 2012-12-31, 2012-12-30.... I need to select a column which gives the prior Period of Date, Prior Year End. I am using Db2 as the database.
1. Get the Prior Period calculation. For the First period, it should give as zero (0) and for the remaining periods it should fetch the prior period.
2. Get the Prior Year End value (E.g. 2012-12-31 )