问题
I have a table like below which would have the product description
╔════╦══════════════╦══════╗ ║ Id ║ name ║ price║ ╠════╬══════════════╬══════╣ ║ 1 ║ Apple ║ 23 ║ ║ 2 ║ shirt ║ 148 ║ ║ 3 ║ computer ║ 101 ║ ║ 4 ║ printer ║ 959 ║ ╚════╩══════════════╩══════╝
and another table which is holding the attributes like linked by the ID
╔════╦══════════════╦══════╗ ║ Id ║ attr_name ║ Value║ ╠════╬══════════════╬══════╣ ║ 1 ║ color ║ red ║ ║ 1 ║ size ║ xl ║ ║ 1 ║ brand ║ App ║ ║ 2 ║ color ║ blue║ ║ 2 ║ size ║ l ║ ║ 3 ║ color ║ blue║ ║ 3 ║ size ║ xxl ║ ║ 3 ║ brand ║ HP ║ ╚════╩══════════════╩══════╝
Is there any possible way to bring a table like below if I know the attribute name is going to be only color size and brand
╔════╦══════════╦═══════╦═══════╦══════╦══╗ ║ id ║ name ║ color ║ brand ║ size ║ ║ ╠════╬══════════╬═══════╬═══════╬══════╬══╣ ║ 1 ║ apple ║ red ║ app ║ xl ║ ║ ║ 2 ║ shirt ║ blue ║ ║ l ║ ║ ║ 3 ║ computer ║ blue ║ HP ║ XXL ║ ║ ║ 4 ║ printer ║ ║ ║ ║ ║ ╚════╩══════════╩═══════╩═══════╩══════╩══╝
回答1:
You should be able to use an aggregate function with a CASE expression to convert the rows into columns:
select d.id,
d.name,
max(case when a.attr_name = 'color' then a.value end) color,
max(case when a.attr_name = 'brand' then a.value end) brand,
max(case when a.attr_name = 'size' then a.value end) size
from product_description d
inner join product_attributes a
on d.id = a.id
group by d.id, d.name;
See SQL Fiddle with Demo.
Since you are using Oracle 11g, then you can use the PIVOT function to get the result:
select id, name, Color, Brand, "Size"
from
(
select d.id, d.name,
a.attr_name, a.value
from product_description d
inner join product_attributes a
on d.id = a.id
) src
pivot
(
max(value)
for attr_name in ('color' as Color,
'brand' as Brand,
'size' as "Size")
) p;
See SQL Fiddle with Demo
来源：https://stackoverflow.com/questions/21836757/join-pivot-items-with-eav-table