 ,  union:
WorkId	CompId	DispId	PrintId	ScanId	UserId
1	1				
1		1			
1		2			
1				1	
1					1
1					2
1					3
2	2				
2		3			
2		6			
2			1		
2			2		
2					4
3	3				
3	4				
3	5				
3	6				
3		4			
3		5			
3		7			
3			3		
3			4		
3			5		
3			6		
3				2	
3				3	