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mysql教程 sql  distinct  删除重复记录

如何在mysql中使用distinct关键字过滤在一个select语句的结果列表重复值

如果你在查询数据时想删除重复的数据，可以利用distinct关键字过滤重复值，下面看下distinct用法。

select distinct column_name from table_name;

让我们来看看一个简单的例子，我们有一个汽车列表。每辆车都有一个id，品牌，类型和颜色，但现在我们只是简单的列出所有品牌：

select brand from car;
the result is:audi                                                                                                                                    audi                                                                                                                                    audi                                                                                                                                    bmw                                                                                                                                    bmw                                                                                                                                    lexus                                                                                                                                    lexus    

正如你可以看到品牌显示几次。但是我们要的是知道有多少不同的品牌，在db的。要获得此扩展查询，如下所示

select distinct brand from car;
 the result is:
 audi                                                                                                       bmw
 lexus

 
如果你想知道有多少次不同的品牌,那么我们就必须用count group by 来实现了，下面看实例

select brand, count(brand) from car group by brand;
and the result is:brand  count(brand)        
audi  3                   
bmw  2                   
lexus  2

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