Merge two dataset into one with nulls in some columns

Question

Hi All
I am getting a problem in merging two datasets into one. Both datasets have the same schema, structure but different data. One of the datasets have data with null values in some columns. But I want them to merge and the final result should be that one of the dataset has all the rows.
Fyi, the two datasets were populated with data from excel files. Both excel files have same columns. But they can have null values in some of the columns.
Please help me to resolve this issue.