I have the following JPA query: select NEW java.lang.String(c.country) from Contact c group by c.country order by c.country
When one of the rows in Contact table holds null value for country field, the String constructor in the JPA query above throws a NullPointerException.
As a null value in the country field in Contact table is allowed, is there any way to prevent it via code and still use a named query?
关于什么
select c.country from Contact c where c.country is not null group by c.country order by c.country
A group by makes no sense here, since you don't have any aggregate function in the select clause. Calling the string constructor is also useless.
Just use
select c.country from Contact c order by c.country
If the goal of the group by is to select distinct values, use distinct
:
select distinct c.country from Contact c order by c.country
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.