Question

我需要每页显示100个成员。由于会员的电话号码多，我必须为每个会员选择第一个电话号码。

以下是查询成员的每个电话号码的查询：

    SELECT * FROM 
    (     
          SELECT
          row_number() over(order by(1)) rn, 
          NAME, PHONE    
                FROM MEMBERS t0     
                LEFT OUTER JOIN MEMBER_IDENTITY ON MEMBER_IDENTITY.ID=t0.ID 
                LEFT JOIN MEMBER_PHONE ON MEMBER_PHONE.MEMBER_ID=t0.ID    
                WHERE
          NAME LIKE 'U%' 
          ORDER BY NAME ASC 
    )      
WHERE rn >= 0
AND rn <= 100

我如何选择第一个 - 或MAX，等电话号码？

Answer 1

您可以进行子查询以检索电话号码及其每个成员的行号，然后过滤掉其中的第一个：

SELECT  * 
FROM    (
        SELECT    row_number() OVER (ORDER BY name ASC) rn, 
                  name, 
                  phone
        FROM      members t0 
        LEFT JOIN member_identity 
               ON member_identity.id = t0.id 
        LEFT JOIN (
                  SELECT member_id,
                         phone
                         row_number() OVER (PARTITION BY member_id ORDER BY (1)) ph_rn
                  FROM   member_phone
                  ) member_phone
               ON member_phone.member_id = t0.id
              AND ph_rn = 1
        WHERE     name LIKE 'U%' 
        ORDER BY  name ASC
        )
WHERE   rn BETWEEN 0 AND 100

我会：

使用相同的顺序将rn值确定为结果集（ORDER BY name ASC），否则订单在各页之间将不一致;
在外BETWEEN条件中使用WHERE，但第一页不需要下限条件（0）。

Answer 2

当您切换到MAX时，您可以直接在名称上应用ROW_NUMBER（在 GROUP BY / HAVING之后，窗口化聚合函数被计算）：

SELECT * FROM ( SELECT row_number() over (ORDER BY NAME ASC) rn, NAME, MAX(PHONE) FROM MEMBERS t0 LEFT OUTER JOIN MEMBER_IDENTITY ON MEMBER_IDENTITY.ID=t0.ID LEFT JOIN MEMBER_PHONE ON MEMBER_PHONE.MEMBER_ID=t0.ID WHERE NAME LIKE 'U%' GROUP BY NAME ) WHERE rn >= 0 AND rn <= 100

或将聚合移动到派生表中：

SELECT * FROM ( SELECT row_number() over (ORDER BY NAME ASC) rn, NAME, PHONE FROM MEMBERS t0 LEFT OUTER JOIN MEMBER_IDENTITY ON MEMBER_IDENTITY.ID=t0.ID LEFT JOIN ( SELECT MEMBER_ID, MAX(PHONE) AS PHONE FROM MEMBER_PHONE GROUP BY NAME ) MEMBER_PHONE ON MEMBER_PHONE.MEMBER_ID=t0.ID WHERE NAME LIKE 'U%' ) WHERE rn >= 0 AND rn <= 100

获取第一个电话号码的行

2 个答案: