SELECT *
FROM (SELECT m.ID, VMat AS V, NPart AS N, MDescription AS Description FROM tblMain AS m 
LEFT JOIN (SELECT MatID, VMat, NPart, MDescription FROM tblMaterial) AS mat ON m.ID = mat.MatID
UNION ALL
SELECT m.ID, VLab AS V, NLabPos AS N, LDescription AS Description FROM tblMain AS m 
LEFT JOIN (SELECT LabID, VLab, NLabPos, LDescription FROM tblLabour) AS lab ON m.ID = lab.LabID) t WHERE t.V = 1 GROUP BY t.ID, t.V, t.N, t.Description

SELECT m.ID, NClaim, LEFT(TypeClaim, 4) AS TypeClaim, DRepair, NZN, VIN, Customer, PrObr, KI, DamageType
 FROM tblMain AS m LEFT JOIN tblDamage AS d ON m.ID = d.DamID
LEFT JOIN (SELECT *
FROM (SELECT m.ID, VMat AS V, NPart AS N, MDescription AS Description FROM tblMain AS m 
LEFT JOIN (SELECT MatID, VMat, NPart, MDescription FROM tblMaterial) AS mat ON m.ID = mat.MatID
UNION ALL
SELECT m.ID, VLab AS V, NLabPos AS N, LDescription AS Description FROM tblMain AS m 
LEFT JOIN (SELECT LabID, VLab, NLabPos, LDescription FROM tblLabour) AS lab ON m.ID = lab.LabID) t WHERE t.V = 1 GROUP BY t.ID, t.V, t.N, t.Description) AS temp ON m.ID = temp.ID

SELECT m.ID, NClaim, LEFT(TypeClaim, 4) AS TypeClaim, DRepair, NZN, VIN, Customer, PrObr, KI, DamageType, temp.V, temp.N, temp.Description
FROM tblMain AS m LEFT JOIN tblDamage AS d ON m.ID = d.DamID
LEFT JOIN (SELECT *
FROM (SELECT m.ID, VMat AS V, NPart AS N, MDescription AS Description FROM tblMain AS m 
LEFT JOIN (SELECT MatID, VMat, NPart, MDescription FROM tblMaterial) AS mat ON m.ID = mat.MatID
UNION ALL
SELECT m.ID, VLab AS V, NLabPos AS N, LDescription AS Description FROM tblMain AS m 
LEFT JOIN (SELECT LabID, VLab, NLabPos, LDescription FROM tblLabour) AS lab ON m.ID = lab.LabID) t WHERE t.V = 1 GROUP BY t.ID, t.V, t.N, t.Description) AS temp ON m.ID = temp.ID