erd concepts
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when designing the erd , let's consider the following case : we have two entities : (management_board) and (person) , a person can't be a member in more than one management board at once , but he can be a member in management_board_1 in 2011 , and then a member in management_board_2 in 2012 , so , the relation between entities : (management_board) and (person) , is it (one to many) or (many to many) ?
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when designing the erd , let's consider the following case : we have two entities : (management_board) and (person) , a person can't be a member in more than one management board at once , but he can be a member in management_board_1 in 2011 , and then a member in management_board_2 in 2012 , so , the relation between entities : (management_board) and (person) , is it (one to many) or (many to many) ?
If he can be in only 1 MB at a time then it is one to many. If you need a history of membership then it requires a different design, either m-m or an archive record.
Never underestimate the power of human stupidity RAH