I need to produce the column "required" in the following table using SQL without using loops and correlated sub queries. Is this possible in SQL 2008?
Date Customer Value Required Rule
20100101 1 12 12
20100101 2 0 If no value assign 0
20100101 3 32 32
20100101 4 42 42
20100101 5 15 15
20100102 1 12 Take last known value
20100102 2 0 Take last known value
20100102 3 39 39
20100102 4 42 Take last known value
20100102 5 16 16
20100103 1 13 13
20100103 2 24 24
20100103 3 39 Take last known value
20100103 4 42 Take last known value
20100103 5 21 21
20100104 1 14 14
20100104 2 24 Take last known value
20100104 3 39 Take last known value
20100104 4 65 65
20100104 5 23 23
Basically I am filling empty "Value" cells with last know value for that customer. Remember the last row may not have a valid value, so you will have to pick it from the row before that with a valid value.