如何在 sql 中转换和 pivot

Question

我有一张如下表

我想计算每个产品并对其进行改造

t1

customer product
A            a
A            b
A            c 
B            a
B            c
C            a

我想要的结果如下，

customer  product(a) product(b) product(c)
A           1           1           1
B           1           0           1
C           1           0           0

有什么办法可以变身？？

谢谢

Answer 1

您可以使用conditional aggregation

select customer,count(case when product='a' then 1 end) as product_a,
count(case when product='b' then 1 end) as product_b,
count(case when product='c' then 1 end) as product_c
from tablename
group by customer

另一种选择可能是使用pivot operator -

SELECT * FROM t
 PIVOT (count(product) FOR product IN 
    ( 'a' AS product_a, 'b' AS  product_b, 'c' AS product_c ))

Answer 2

还存在另一种条件聚合方法，该方法通过使用传统的DECODE() function 特别适用于 Oracle DB 进行操作。 如果产品与文字（ 'a' 、 'b'或'c' ）匹配，则在哪个值中求和，否则（ else情况下）零返回：

SELECT customer,
       SUM(DECODE(product , 'a', 1, 0 )) AS product_a,
       SUM(DECODE(product , 'b', 1, 0 )) AS product_b,
       SUM(DECODE(product , 'c', 1, 0 )) AS product_c
  FROM t
 GROUP BY customer

演示

Answer 3

SQLFiddle

select * from table1 
pivot(count(product) 
      for product 
      in ('a' "product(a)", 'b' "product(b)", 'c' "product(c)", 'd' "product(d)"));