CREATE TABLE Company $($

person$\_$id int PRIMARY KEY,

person$\_$Name VARCHAR$(255),$

department$\_$ID VARCHAR$(255),$

company$\_$Name VARCHAR$(255),$

isAstMgr BOOLEAN,

isMgr BOOLEAN,

isGnrMgr BOOLEAN,

FOREIGN KEY $($deparment$\_$ID$,$company$\_$Name$)$ REFERENCES Holding$($deparment$\_$ID$,$company$\_$Name$)$

$)$;

How to check condition that a person can only have one role which is AstMgr or Mgr or GnrMgr$.$ Two or more roles are not possible per person.

There may be several AstMgr or Mgr for a specific $($deparment$\_$ID$,$company$\_$Name$).$

If there is a GnrMgr for a specific $($deparment$\_$ID$,$company$\_$Name$)$ there will not be other GnrMgr for same company.

How to write a DDL to check isGnrMgr column and not to allow to enter second GnrMgr for the same unique $($deparment$\_$ID$,$company$\_$Name$)$