SQLServer查詢去重

第一種： Distinct

 SELECT Distinct列名稱 FROM 表名稱

e.g. 

 

 SELECT Distinct userid FROM UserInfo;

但是Distinct只能放在字段的開頭，如果多個字段，將不會去重。

SELECT Distinct userid, id FROM UserInfo;

 

第二種，row_number() over() 函數

SELECT
 top 10
  *
FROM
(
SELECT
     *
FROM
    (
    SELECT
        a,b,c,d,
        ROW_NUMBER () OVER ( Partition BY a ORDER BY b ) AS row 
    FROM
        tab_name1
    ) p 
WHERE
p.row =1
) as aa
LEFT JOIN tab_name2 b ON aa.xx = b.xx

 

參考：

https://blog.csdn.net/qq_36330228/article/details/84174817