如何在查询中的列名中获取列数据？

Question

如果我有下表：

 Cust Prod     Qty
===== ====     ===
 Bob   Apple    3
 Bob   Orange   2
 Bob   Banana   4
 Rob   Apple    2
 Rob   Orange   1
 Bob   Apple    2

如何以表格数据作为列名获得以下结果：

Prod   Bob Rob
====== === ===
Apple    5   2
Orange   2   1
Banana   4  null

Answer 1

您可以在MSSQL中使用PIVOT或以下方式：

SELECT
PROD,
SUM(CASE WHEN Cust='Bob' THEN Qty ELSE 0 END) as Bob,
SUM(CASE WHEN Cust='Rob' THEN Qty ELSE 0 END) as Rob

FROM T
GROUP BY PROD

SQLFiddle demo

Answer 2

SELECT * from t
pivot
(
  sum(Qty)
  for [Cust] in ([Bob],[Rob])
)as p;
GROUP BY PROD

fiddle demo