Mapping table problem

HI guys
I need to put multiple coniditions on my table based on some combinations.

Here is my main table-

Practitioner	DHBName	PHOName	Practicename	PractitionerName	Locum	YCount	NCount
4	Canterbury DHB	Partnership Health (Canterbury)-596721	Linwood Avenue Medical Centre	Christine Abbasi	No	0	1
32	Canterbury DHB	Partnership Health (Canterbury)-596721	Felicia House Clinic (Pearson)	Nicci Pavey	No	0	1
197	Canterbury DHB	Partnership Health (Canterbury)-596721	Woodham Road Health Care	Peggy Shelton-Agar	No	0	1
394	Hawkes Bay DHB	Hawkes Bay PHO Limited-587862	The Doctors Napier	John Laird	YES	1	0
549	Canterbury DHB	Partnership Health (Canterbury)-596721	Linwood Avenue Medical Centre	Denise Armstrong	No	0	1
1286	Canterbury DHB	Partnership Health (Canterbury)-596721	Darfield Medical Centre Limited	Katherine Muscroft-Taylor	No	0	1
1501	Counties-Manukau DHB	Procare Network Manukau Limited-573183	Manukau City Health Centre	Caroline Shephard	YES	1	0
1932	Hawkes Bay DHB	Hawkes Bay PHO Limited-587862	Clive Medical Centre Ltd	Karen Irwin	YES	1	0
2226	Canterbury DHB	Partnership Health (Canterbury)-596721	Sumner Health Centre	Anne Scott	No	0	1
3243	Waitemata DHB	Harbour PHO Ltd-610733	Byron Medical	Rex Livingstone Sinclair	No	0	1
3263	Canterbury DHB	Partnership Health (Canterbury)-596721	Sumner Health Centre	Peter Wynn Nicholson	No	0	1
3381	Otago DHB	Otago Southern Region Primary Health Organisation-597004	Dr Visagie's Practice	Fay Young	NO	0	1

Here is my mapping table-

I have to add an additional column called 'percentage' in my main table by refering the mapping table.

For ex for a particular practitioner, Locum flag is 'Yes', nocount is 1 and yes count is 1, then percentage should be '0.25'

How should I do this??