Question

我有两张桌子

UserInfo
ContactInfo

我的表格结构如下：

的UserInfo

 UserId   Name
 1        Sandeep
 2        James
 3        Vishal

的ContactInfo

    Id UserId   Email             Mobile 
    1  1        e1@somemail.com   111111
    2  1        e2@somemail.com   222222
    3  3        v1@somemail.com   010101

现在我正在寻找下面的结果

结果

    UserId UserName   Email1          Mobile1   Email2          Mobile2
      1    Sandeep    e1@somemail.com 111111    e2@somemail.com 222222
      2    James      NULL            NULL      NULL             NULL
      3    Vishal     v1@somemail.com 010101    NULL             NULL

注意： UserInfo与ContactInfo之间的一对多关系

任何人都可以帮助我完成它吗？非常感谢您的回复。

Answer 1

你的桌子结构不是很好。例如，如果您的用户有一封电子邮件但有两个手机号码怎么办？您与哪个手机号码关联？这种关联没有意义。这些都是当前形式的数据的准确表示：

1

ID | UserId | Email     | Mobile
1  | 1      | a@a.com   | 111111
2  | 1      | NULL      | 222222

2

ID | UserId | Email     | Mobile
1  | 1      | NULL      | 111111
2  | 1      | a@a.com   | 222222

3

ID | UserId | Email     | Mobile
1  | 1      | NULL      | 111111
2  | 1      | NULL      | 222222
3  | 1      | a@a.com   | NULL

相反，请考虑这样的结构：

ID | UserId | Type      | Mobile
1  | 1      | Mobile    | 111111
2  | 1      | Mobile    | 222222
3  | 1      | Email     | a@a.com

还有其他改进，但我离题了。要以当前状态回答您的问题，以下查询应该有效：

SELECT     U.Name,
           CI1.Email as Email1,
           CI1.Mobile as Mobile1,
           CI2.Email as Email2,
           CI2.Mobile as Mobile2

FROM       UserInfo U

LEFT JOIN  (
           SELECT   UserID,
                    Email,
                    Mobile,
                    ROW_NUMBER() OVER (PARTITION BY UserID ORDER BY ID) as row
           FROM     ContactInfo
           ) CI1
ON         U.UserID = CI1.UserID
AND        CI1.row = 1


LEFT JOIN  (
           SELECT   UserID,
                    Email,
                    Mobile,
                    ROW_NUMBER() OVER (PARTITION BY UserID ORDER BY ID) as row
           FROM     ContactInfo
           ) CI2
ON         U.UserID = CI1.UserID
AND        CI1.row = 2

Answer 2

如果我理解正确，并且您只想显示每个给定用户的最低ID的ContactInfo记录，我会执行以下操作：

SELECT  ci.UserId, ui.Name AS UserName, ci.*
  FROM  UserInfo ui
 INNER  JOIN (
        SELECT  ci.UserId AS UserId, MIN(ci.Id) AS Id
          FROM  ContactInfo ci
         GROUP  BY ci.UserId
        ) AS q ON (q.UserId = ui.UserId)
 INNER  JOIN ContactInfo ci ON (ci.Id = q.Id)

编辑：使用OVER PARTITION BY通常也可以，但我通常更喜欢使用嵌套查询，因为它们通常有更好的执行计划。

Answer 3

您可以执行dynamic crosstab来实现此目标。

DECLARE @sql NVARCHAR(MAX)

SELECT @sql = 
'SELECT
      u.UserId
    , u.Name' + CHAR(10)

SELECT @sql = @sql +
'   , MAX(CASE WHEN t.rn = ' + CONVERT(VARCHAR(10), rn) +' THEN t.Email END) AS ' 
        + QUOTENAME('Email' + CONVERT(VARCHAR(10), rn)) + CHAR(10) +
'   , MAX(CASE WHEN t.rn = ' + CONVERT(VARCHAR(10), rn) +' THEN t.Mobile END) AS ' 
        + QUOTENAME('Mobile' + CONVERT(VARCHAR(10), rn)) + CHAR(10)
FROM (
    SELECT DISTINCT
        rn = ROW_NUMBER() OVER(PARTITION BY UserId ORDER BY Id)
    FROM ContactInfo
)t
-- Add filter here for ROW_NUMBER, e.g. starting from the 25th row to 50th
WHERE rn BETWEEN 25 AND 50

SELECT @sql = @sql +
'FROM UserInfo u
LEFT JOIN (
    SELECT *,
        rn = ROW_NUMBER() OVER(PARTITION BY UserId ORDER BY Id)
    FROM ContactInfo
)t
    ON t.UserId = u.UserId
    -- Add filter here for ROW_NUMBER, e.g. starting from the 25th row to 50th
    AND rn BETWEEN 25 AND 50
GROUP BY u.UserId, u.Name
ORDER BY u.UserId, u.Name'

PRINT @sql
EXEC(@sql)

DEMO

根据ID选择table1中的所有行以及table2中所有匹配的行

3 个答案: