mysql sql DISTINCT 删除反复记录[网站编程]

如安在mysql中利用distinct关键字过滤在一个select语句的后果列表反复值

假如你在查询数据时想删除反复的数据,可以操纵distinct关键字过滤反复值,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,范例和颜色,但目前我们只是简单的列出全部品牌:

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差别的品牌,在db的.要得到此扩大查询,以下所示

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

 
假如你想知道有多少次差别的品牌,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