DB2 - Is there a simple way to get “previous valid value”?

You can use LATERAL JOIN, DB2 is not yet on SQLFiddle, following is its equivalent in SQL Server. LATERAL is equivalent to SQL Server's APPLY.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.