如果您只对问题中显示的两列内容感兴趣，有一个非常简单的解决方案：

select product_id, min(availability) feasible
from tbl group by product_id

看看这里demo:. http://rextester.com/gmt80394

--insert into test(product_id, availability) values (1,true),(1,false),(2,true),(2,true);

select distinct product_id 
from test
where product_id not in (
    select product_id
    from test
    group by product_id, availability
    having availability=false
)

使用子查询和 case when 条款

select t.productid,case when availability ='true' 
    then 'product available' else 'product not available' end as feasibility 
   from 
    (
        select  productid,availability from your_table
        group by  productid,availability
    ) as t