mysql sql DISTINCT 重複資料刪除記錄

mysql教程 sql  distinct  重複資料刪除記錄

如何在mysql中使用distinct關鍵字過濾在一個select語句的結果清單重複值

如果你在查詢資料時想重複資料刪除的資料，可以利用distinct關鍵字過濾重複值，下面看下distinct用法。

select distinct column_name from table_name;

讓我們來看看一個簡單的例子，我們有一個汽車列表。每輛車都有一個id，品牌，類型和顏色，但現在我們只是簡單的列出所有品牌：

 

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

                                                                                                         

正如你可以看到品牌顯示幾次。但是我們要的是知道有多少不同的品牌，在db的。要獲得此擴充查詢，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,那麼我們就必須用count group by 來實現了，下面看執行個體

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