TABLE_A

Rev     ChangedBy
-----------------------------
1       A
2       B
3       C

TABLE_B

Rev Words      ID
----------------------------
1 description_1   52
1 history_1         54
2 description_2   52
3 history_2         54

Words column datatype is ntext.

TABLE_C

ID Name
-----------------------------
52 Description
54 History

OUTPUT

Rev ChangedBy Description        History  
------------------------------------------------
1     A   description_1      history_1
2     B   description_2      history_1
3     C   description_2      history_2

Description and History column will have the previous known values if they dont have value for that Rev no. i.e. Since for Rev no. 3 Description does not have an entry in TABLE_B hence the last known value description_2 appears in that column for Rev no. 3 in the output.