如何操作MySQL全文搜索相关性，使一个字段比另一个字段更有价值?

Suppose I have two columns, keywords and content. I have a fulltext index across both. I want a row with foo in the keywords to have more relevance than a row with foo in the content. What do I need to do to cause MySQL to weight the matches in keywords higher than those in content? Suppose I have two columns, keywords and conten