几行信息到一行

Question

您好，我需要合并 2 个包含客户信息的表。 Table 2 告诉我们是否有关于电子邮件、地址和电话号码的客户信息，但数据是结构化的，因此每个客户有 3 行。有没有办法合并这两个表，以便每个客户只得到一行，但包含所有联系信息？

Table 1:

id  customerID  ... ...

1   11 

2   99

和Table 2:

id  customerID  Channel Y_N

1   11          Email    Y

2   11          Address  Y

3   11          Phone    N

4   99          Email    N

5   99          Address  Y

6   99          Phone    N

我的代码是这样的

TABLE 1
left join(
    select customerID, 
    case when Y_N='Y' and Channel='Email' then 1 else 0 end as Email
    FROM table2 
    where Channel='Email')a
    on table1.customerID=a.customerID
Left join(
    select customerID, 
    case when Y_N='Y' and Channel='Address' then 1 else 0 end as Address
    FROM table2
    where Channel='Address') b
    on table1.customerID=b.customerID
Left join(
    select customerID, 
    case when Y_N='Y' and Channel='Phone' then 1 else 0 end as Phone
    FROM table2
    where Channel='SMS') c
    on  table1.customerID=c.customerID

哪个确实能完成这项工作，但如果我以后必须再做一次，有没有更聪明的方法？

谢谢

Answer 1

好吧，如果它有效，为什么要改变它？但如果你必须这样做，也许是这样的：

SELECT
    c.*,
    IF(e.Y_N='Y',1,0) AS Email,
    IF(a.Y_N='Y',1,0) AS Address,
    IF(p.Y_N='Y',1,0) AS Phone
FROM table1 AS c
   LEFT JOIN table2 AS e ON(c.customerID=e.customerID AND Channel='Email')
   LEFT JOIN table2 AS a ON(c.customerID=a.customerID AND Channel='Address')
   LEFT JOIN table2 AS p ON(c.customerID=p.customerID AND Channel='Phone')

另外，我真的看不出有什么好的理由让每个客户在表 2 中有三行。如果可能的话，你最好把它改成

customerID|Email|Address|Phone
    11    |  1  |   1   |  0
    99    |  0  |   1   |  0

这样你就可以做到

SELECT * FROM table1 AS a LEFT JOIN table2 AS b ON a.customerID=b.customerID

Answer 2

如果您希望将来有新频道，您可以使用它来动态添加频道作为列：

DECLARE @SearchList     varchar(MAX)
DECLARE @sql            varchar(MAX)

select @SearchList = COALESCE(@SearchList, '') + ', [' + cast(Channel as VARCHAR(100)) + ']' 
from (select distinct channel from #table2) a

set @sql = 'select CustomerID, ' + RIGHT(@SearchList, LEN(@SearchList)-1) +'
from
(select CustomerID, Channel, Y_N
    from #table2) as t
pivot
(
    max(Y_N)
    for Channel in (' + RIGHT(@SearchList, LEN(@SearchList)-1) + ')
) as pvt'

exec(@sql)

Answer 3

您可以用单个 usong 条件聚合 (=pivot) 替换这三个联接：

TABLE1
left join(
    select customerID, 
       max(case when Y_N='Y' and Channel='Email' then 1 else 0 end) as Email
       max(case when Y_N='Y' and Channel='Address' then 1 else 0 end) as Address
       max(case when Y_N='Y' and Channel='Phone' then 1 else 0 end) as Phone
    FROM table2 
    GROUP BY 1) a
    on table1.customerID=a.customerID

这可能更有效，请查看说明...

几行信息到一行

Several rows with info to a single row

sql

teradata