ID           Status          W_ID
1          In Progress        7
2          In Progress        5
3          Complete           5
4          In Progress       NULL
5          Complete           7

ID           Status          W_ID
2          In Progress        5
4          In Progress       NULL

Select * from table where Status = 'In Progress' and  (W_ID is NULL or W_ID = 5)

WHERE Status = 'In Progress' AND (W_ID IS NULL OT W_ID = 5)

WHERE Status = 'In Progress' AND ISNULL(W_ID,5)= 5