这种类型的数据转换需要使用pivot 和unpivot 函数来完成。由于您的访问将是未知的，因此您将需要使用动态 sql。但首先，我将向您展示如何使用硬编码的值构建查询，以便更容易理解该过程的工作原理。
首先，您需要 UNPIVOT date 和 weight 列，以便值在同一列中。这可以使用UNION ALL 查询或 unpivot 函数来完成：
反透视：
select patientid, name, rn, col, value
from
(
select p.patientid, p.name, convert(char(5), v.date, 110) date,
cast(v.weight as char(5)) weight,
row_number() over(partition by PatientID_FK order by date) rn
from patients p
left join visits v
on p.patientid = v.PatientID_FK
) src
unpivot
(
value
for col in (date, weight)
) unpiv
见SQL Fiddle with Demo。此查询的结果将 date 和 weight 列的值放入具有多行的单个列中。请注意，我对记录应用了row_number()，这样您就可以知道每次访问的值：
| PATIENTID | NAME | RN | COL | VALUE |
-------------------------------------------
| 1 | James | 1 | date | 01-01 |
| 1 | James | 1 | weight | 220 |
| 1 | James | 2 | date | 02-01 |
| 1 | James | 2 | weight | 210 |
枢轴：
下一步是将PIVOT 函数应用于col 列中的项目，但首先我们需要更改名称，以便它为您提供所需的名称。
为此，我稍微更改了SELECT 语句以将行号添加到列名：
select patientid, name, 'Visit'+col + cast(rn as varchar(10)) new_col,
value
from ...
这将为您提供新名称，这些名称是您想要作为列的名称：
Visitdate1
Visitweight1
Visitdate2
Visitweight2
到PIVOT，如果您对值进行硬编码，您的查询将如下所示：
select *
from
(
select patientid, name, 'Visit'+col + cast(rn as varchar(10)) new_col,
value
from
(
select p.patientid, p.name, convert(char(5), v.date, 110) date,
cast(v.weight as char(5)) weight,
row_number() over(partition by PatientID_FK order by date) rn
from patients p
left join visits v
on p.patientid = v.PatientID_FK
) src
unpivot
(
value
for col in (date, weight)
) unpiv
) s1
pivot
(
max(value)
for new_col in (Visitdate1,Visitweight1,
Visitdate2,Visitweight2)
) piv
见SQL Fiddle with Demo。
动态枢轴：
现在我已经解释了如何设置背后的逻辑，您将希望使用动态 sql 实现相同的过程。您的动态 sql 版本将是：
DECLARE @colsUnpivot AS NVARCHAR(MAX),
@query AS NVARCHAR(MAX),
@colsPivot as NVARCHAR(MAX)
select @colsUnpivot = stuff((select ', '+quotename(C.name)
from sys.columns as C
where C.object_id = object_id('visits') and
C.name not in ('PatientID_FK')
for xml path('')), 1, 1, '')
select @colsPivot = STUFF((SELECT ',' + quotename('Visit'+c.name
+ cast(v.rn as varchar(10)))
from
(
select row_number() over(partition by PatientID_FK order by date) rn
from visits
) v
cross apply sys.columns as C
where C.object_id = object_id('visits') and
C.name not in ('PatientID_FK')
group by c.name, v.rn
order by v.rn
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set @query
= 'select *
from
(
select patientid, name, ''Visit''+col + cast(rn as varchar(10)) new_col,
value
from
(
select p.patientid, p.name, convert(char(5), v.date, 110) date,
cast(v.weight as char(5)) weight,
row_number() over(partition by PatientID_FK order by date) rn
from patients p
left join visits v
on p.patientid = v.PatientID_FK
) x
unpivot
(
value
for col in ('+ @colsunpivot +')
) u
) x1
pivot
(
max(value)
for new_col in ('+ @colspivot +')
) p'
exec(@query)
见SQL Fiddle with Demo
两个版本的结果是：
| PATIENTID | NAME | VISITDATE1 | VISITWEIGHT1 | VISITDATE2 | VISITWEIGHT2 |
-----------------------------------------------------------------------------
| 1 | James | 01-01 | 220 | 02-01 | 210 |