逻辑运算符
可以合并两个或更多条件。条件必须由 AND 或 OR 相关联,例如:
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                                        salary = 40000 AND exempt = 1逻辑 NOT 运算符用于反转含义,例如:
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                                        NOT (salary = 40000 AND exempt = 1)示例
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                                        SELECT * FROM Sales_Data WHERE Sales_Data.Company_Name
   NOT LIKE '%University' AND Sales_Data.Amount > 3000
SELECT * FROM Sales_Data WHERE (Sales_Data.Company_Name
   LIKE '%University' OR Sales_Data.Amount > 3000)
   AND Sales_Data.Salesperson_ID = 'SP-1'