在 SQL t 中使用 Pivot

Question

我很少不得不在 SQL 中使用 pivot，而且我很难理解它。我有查询生成 table 的患者和医疗机构的保险。我想要 return 一行显示患者拥有的所有保险。

示例数据：

ID  Insurance
1840    Medicaid Of New York
1841    Affinity Health Plan
1841    Medicaid Of New York
1842    Fidelis Care
1842    Medicaid Of New York

目标是像这样显示数据：

我了解 pivot 的基本功能，但没有太多时间弄清楚如何实现上述结果。我还没有取得任何接近工作成果的成果，这可能是缺乏经验或此时疲劳。任何帮助将不胜感激。

Answer 1

如果您最多有两个值（如您的示例数据和结果所建议的那样），您可以使用 min() 和 max():

select id,
       min(insurance) as insurance1,
       (case when min(insurance) <> max(insurance) then max(insurance)
        end) as insurance2
from t
group by id;

Answer 2

像这样

with data as (
select id,insurance ,row_number() over ( partition by id order by insurance) rowid 
)


select d.id , [1] as ins1,[2] ins2,[3]ins3,[4] ins4
from data d
pivot 
(max(insurance) 
for rowid in ([1],[2],[3],[4])
)pv

Answer 3

这就是您要查找的内容。这将根据需要展平您的记录。

SELECT 
    ID, Insurance1, Insurance2, Insurance3, Insurance4
FROM (  SELECT 
            ID, 
            Insurance,
            RN = 'Insurance' + 
            CAST(ROW_NUMBER() OVER(PARTITION BY ID ORDER BY Insurance) AS CHAR(1))
        FROM MyDB.MySchema.MyTable
) AS d
PIVOT(
    MAX(Insurance) 
        for RN 
            in (Insurance1, Insurance2, Insurance3, Insurance4)
) AS p;

Answer 4

我更喜欢条件聚合：

SELECT  ID,
        MAX(CASE WHEN RN = 1 THEN INSURANCE ELSE '' END) AS INSURANCE1,
        MAX(CASE WHEN RN = 2 THEN INSURANCE ELSE '' END) AS INSURANCE2,
        MAX(CASE WHEN RN = 3 THEN INSURANCE ELSE '' END) AS INSURANCE3,
        MAX(CASE WHEN RN = 4 THEN INSURANCE ELSE '' END) AS INSURANCE4
FROM (
      SELECT  ID,
              INSURANCE,
              ROW_NUMBER() OVER (PARTITION BY ID ORDER BY INSURANCE) RN
      FROM YourTable
     ) A
GROUP BY ID

This 是关于条件聚合或交叉表的好读物，而不是 PIVOT

在 SQL t 中使用 Pivot

Using Pivot in SQL t

sql

pivot

sql-server-2008-r2